Resolve leftover feedback for IBufferWriter (#1963)

Update the docs based on feedback from #1949 / dotnet/corefx#35554

Author: ahsonkhan

xml/System.Buffers/IBufferWriter`1.xml

@@ -17,7 +17,7 @@
   <Interfaces />
   <Docs>
     <typeparam name="T">The type of the items in the <see cref="T:System.Buffers.IBufferWriter`1" />.</typeparam>
-    <summary>Represents a <typeparamref name="T" /> output sink into which data can be written.</summary>
+    <summary>Represents an output sink into which <typeparamref name="T" /> data can be written.</summary>
     <remarks>To be added.</remarks>
   </Docs>
   <Members>
@@ -67,15 +67,15 @@
         <Parameter Name="sizeHint" Type="System.Int32" />
       </Parameters>
       <Docs>
-        <param name="sizeHint">The minimum length of the returned <see cref="T:System.Memory`1" />. If 0, some, non-empty buffer is returned. </param>
+        <param name="sizeHint">The minimum length of the returned <see cref="T:System.Memory`1" />. If 0, a non-empty buffer is returned. </param>
         <summary>Returns a <see cref="T:System.Memory`1" /> to write to that is at least the requested size (specified by <paramref name="sizeHint" />).</summary>
         <returns>A <see cref="T:System.Memory`1" /> of at least the size <paramref name="sizeHint" />. If <paramref name="sizeHint" /> is 0, returns a non-empty buffer.</returns>
         <remarks>  
           <format type="text/markdown"><![CDATA[  
 
 There is no guarantee that successive calls will return the same buffer or the same-sized buffer.
 
-This must never return <xref:System.Span%601.Empty?displayProperty=nameWithType>, but it can throw <xref:System.OutOfMemoryException> if the requested buffer size is not available.
+This must never return <xref:System.Span%601.Empty?displayProperty=nameWithType>, but it can throw if the requested buffer size is not available.
 
 You must request a new buffer after calling `Advance` to continue writing more data; you cannot write to a previously acquired buffer.
 
@@ -104,15 +104,15 @@ You must request a new buffer after calling `Advance` to continue writing more d
         <Parameter Name="sizeHint" Type="System.Int32" />
       </Parameters>
       <Docs>
-        <param name="sizeHint">The minimum length of the returned <see cref="T:System.Span`1" />. If 0, some, non-empty buffer is returned. </param>
+        <param name="sizeHint">The minimum length of the returned <see cref="T:System.Span`1" />. If 0, a non-empty buffer is returned. </param>
         <summary>Returns a <see cref="T:System.Span`1" /> to write to that is at least the requested size (specified by <paramref name="sizeHint" />).</summary>
         <returns>A <see cref="T:System.Span`1" /> of at least the size <paramref name="sizeHint" />. If <paramref name="sizeHint" /> is 0, returns a non-empty buffer.</returns>
         <remarks>  
           <format type="text/markdown"><![CDATA[
   
 There is no guarantee that successive calls will return the same buffer or the same-sized buffer.
 
-This method must never return <xref:System.Span%601.Empty?displayProperty=nameWithType>, but it can throw <xref:System.OutOfMemoryException> if the requested buffer size is not available.
+This method must never return <xref:System.Span%601.Empty?displayProperty=nameWithType>, but it can throw if the requested buffer size is not available.
 
 You must request a new buffer after calling `Advance` to continue writing more data; you cannot write to a previously acquired buffer.
          ]]></format>