Augment description of ChannelReader.WaitToReadAsync (#3324)

* Augment description of ChannelReader.WaitToReadAsync

* Apply suggestions from code review

Co-Authored-By: Ron Petrusha <[email protected]>

Author: stephentoub

xml/System.Threading.Channels/ChannelReader`1.xml

@@ -166,8 +166,9 @@ Each <xref:System.Collections.Generic.IAsyncEnumerator%601.MoveNextAsync> call t
       <Docs>
         <param name="cancellationToken">A <see cref="T:System.Threading.CancellationToken" /> used to cancel the wait operation.</param>
         <summary>Returns a <see cref="T:System.Threading.Tasks.ValueTask`1" /> that will complete when data is available to read.</summary>
-        <returns>A <see cref="T:System.Threading.Tasks.ValueTask`1" /> that will complete with a <see langword="true" /> result when data is available to read
-            or with a <see langword="false" /> result when no further data will ever be available to be read.</returns>
+        <returns><para>A <see cref="T:System.Threading.Tasks.ValueTask`1" /> that will complete with a <see langword="true" /> result when data is available to read
+            or with a <see langword="false" /> result when no further data will ever be available to be read due to the channel completing successfully.</para>
+            <para>If the channel completes with an exception, the task will also complete with an exception.</para></returns>
         <remarks>To be added.</remarks>
       </Docs>
     </Member>