Update S.T.Unicode.Utf8 APIs to correctly document the isFinalBlock (#3208)

bool.

Author: ahsonkhan

xml/System.Text.Unicode/Utf8.xml

@@ -44,25 +44,25 @@
         <param name="source">A UTF-16 encoded read-only character span.</param>
         <param name="destination">A UTF-8 encoded byte span.</param>
         <param name="charsRead">When the method returns, the number of characters read from <paramref name="source" />.</param>
-        <param name="bytesWritten">When the method returns, the number of characters written to <paramref name="destination" />.</param>
+        <param name="bytesWritten">When the method returns, the number of bytes written to <paramref name="destination" />.</param>
         <param name="replaceInvalidSequences">
           <see langword="true" /> to replace invalid UTF-16 sequences in <paramref name="source" /> with U+FFFD; <see langword="false" /> to return <see cref="F:System.Buffers.OperationStatus.InvalidData" /> if invalid characters are found in <paramref name="source" />.</param>
         <param name="isFinalBlock">
-          <see langword="true" /> if the method should not return <see cref="F:System.Buffers.OperationStatus.InvalidData" />; otherwise, <see langword="false" />.</param>
+          <see langword="true" /> if the method should not return <see cref="F:System.Buffers.OperationStatus.NeedMoreData" />; otherwise, <see langword="false" />.</param>
         <summary>Converts a UTF-16 character span to a UTF-8 encoded byte span.</summary>
         <returns>A value that indicates that status of the conversion.</returns>
         <remarks>
           <format type="text/markdown"><![CDATA[
 
-### Remarks
+## Remarks
 
-This method corresponds to the [UTFEncoding.GetBytes](xref:System.Text.UTF8Encoding.GetBytes%2A) method, except that it has a different calling convention, different error handling mechanisms, and different performance characteristics. 
+This method corresponds to the [UTF8Encoding.GetBytes](xref:System.Text.UTF8Encoding.GetBytes%2A) method, except that it has a different calling convention, different error handling mechanisms, and different performance characteristics. 
 
 If 'replaceInvalidSequences' is `true`, the method replaces any ill-formed subsequences in `source` with U+FFFD in `destination` and continues processing the remainder of the buffer. Otherwise, the method returns <xref:System.Buffers.OperationStatus.InvalidData?displayProperty=nameWithType> if it encounters any ill-formed sequences.
 
 If the method returns an error code, the out parameters indicate how much of the data was successfully transcoded, and the location of the ill-formed subsequence can be deduced from these values.
 
-If 'replaceInvalidSequences' is `true`, the method never returns <xref:System.Buffers.OperationStatus.InvalidData?displayProperty=nameWithType>. If 'isFinalBlock' is `true`, the method is never returns <xref:System.Buffers.OperationStatus.NeedMoreData?displayProperty=nameWithType>.
+If 'replaceInvalidSequences' is `true`, the method never returns <xref:System.Buffers.OperationStatus.InvalidData?displayProperty=nameWithType>. If 'isFinalBlock' is `true`, the method never returns <xref:System.Buffers.OperationStatus.NeedMoreData?displayProperty=nameWithType>.
 
           ]]></format>
         </remarks>
@@ -91,28 +91,28 @@ If 'replaceInvalidSequences' is `true`, the method never returns <xref:System.Bu
         <Parameter Name="isFinalBlock" Type="System.Boolean" />
       </Parameters>
       <Docs>
-        <param name="source">A UTF-8 encoded read-only character span.</param>
-        <param name="destination">A UTF-8 encoded byte span..</param>
+        <param name="source">A UTF-8 encoded read-only byte span.</param>
+        <param name="destination">A UTF-16 encoded character span.</param>
         <param name="bytesRead">When the method returns, the number of bytes read from <paramref name="source" />.</param>
         <param name="charsWritten">When the method returns, the number of characters written to <paramref name="destination" />.</param>
         <param name="replaceInvalidSequences">
           <see langword="true" /> to replace invalid UTF-8 sequences in <paramref name="source" /> with U+FFFD; <see langword="false" /> to return <see cref="F:System.Buffers.OperationStatus.InvalidData" /> if invalid characters are found in <paramref name="source" />.</param>
         <param name="isFinalBlock">
-          <see langword="true" /> if the method should not return <see cref="F:System.Buffers.OperationStatus.InvalidData" />; otherwise, <see langword="false" />.</param>
+          <see langword="true" /> if the method should not return <see cref="F:System.Buffers.OperationStatus.NeedMoreData" />; otherwise, <see langword="false" />.</param>
         <summary>Converts a UTF-8 encoded read-only byte span to a UTF-16 encoded character span.</summary>
         <returns>A value that indicates the status of the conversion.</returns>
         <remarks>
           <format type="text/markdown"><![CDATA[
 
-### Remarks
+## Remarks
 
-This method corresponds to the [UTFEncoding.GetChars](xref:System.Text.UTF8Encoding.GetChars%2A) method, except that it has a different calling convention, different error handling mechanisms, and different performance characteristics. 
+This method corresponds to the [UTF8Encoding.GetChars](xref:System.Text.UTF8Encoding.GetChars%2A) method, except that it has a different calling convention, different error handling mechanisms, and different performance characteristics. 
 
 If 'replaceInvalidSequences' is `true`, the method replaces any ill-formed subsequences in `source` with U+FFFD in `destination` and continues processing the remainder of the buffer. Otherwise, the method returns <xref:System.Buffers.OperationStatus.InvalidData?displayProperty=nameWithType> if it encounters any ill-formed sequences.
 
 If the method returns an error code, the out parameters indicate how much of the data was successfully transcoded, and the location of the ill-formed subsequence can be deduced from these values.
 
-If 'replaceInvalidSequences' is `true`, the method never returns <xref:System.Buffers.OperationStatus.InvalidData?displayProperty=nameWithType>. If 'isFinalBlock' is `true`, the method is never returns <xref:System.Buffers.OperationStatus.NeedMoreData?displayProperty=nameWithType>.
+If 'replaceInvalidSequences' is `true`, the method never returns <xref:System.Buffers.OperationStatus.InvalidData?displayProperty=nameWithType>. If 'isFinalBlock' is `true`, the method never returns <xref:System.Buffers.OperationStatus.NeedMoreData?displayProperty=nameWithType>.
 
           ]]></format>
         </remarks>