Fix minor typo. (#4406)

Appears the description for GetBytes was copied from GetChars and "characters" was missed.

Author: MarkPflug

xml/System.Data.Common/DbDataReader.xml

@@ -599,7 +599,7 @@
         <param name="dataOffset">The index within the row from which to begin the read operation.</param>
         <param name="buffer">The buffer into which to copy the data.</param>
         <param name="bufferOffset">The index with the buffer to which the data will be copied.</param>
-        <param name="length">The maximum number of characters to read.</param>
+        <param name="length">The maximum number of bytes to read.</param>
         <summary>When overridden in a derived class, reads a specified number of bytes from the specified column starting at a specified index and writes them to a buffer starting at a specified position in the buffer.</summary>
         <returns>The actual number of bytes read.</returns>
         <remarks>To be added.</remarks>