Update PipeOptions.xml (dotnet#8693)

Author: halter73

xml/System.IO.Pipelines/PipeOptions.xml

@@ -142,7 +142,7 @@
         <ReturnType>System.Int64</ReturnType>
       </ReturnValue>
       <Docs>
-        <summary>Gets the number of bytes in the <see cref="T:System.IO.Pipelines.Pipe" /> when <see cref="M:System.IO.Pipelines.PipeWriter.FlushAsync(System.Threading.CancellationToken)" /> starts blocking.</summary>
+        <summary>Gets the number of bytes in the <see cref="T:System.IO.Pipelines.Pipe" /> when <see cref="M:System.IO.Pipelines.PipeWriter.FlushAsync(System.Threading.CancellationToken)" /> starts blocking. A value of zero prevents <see cref="M:System.IO.Pipelines.PipeWriter.FlushAsync(System.Threading.CancellationToken)" /> from ever blocking, effectively making the number of bytes in the <see cref="T:System.IO.Pipelines.Pipe" /> unlimited.</summary>
         <value>The number of bytes in the <see cref="T:System.IO.Pipelines.Pipe" /> when <see cref="M:System.IO.Pipelines.PipeWriter.FlushAsync(System.Threading.CancellationToken)" /> starts blocking.</value>
         <remarks>To be added.</remarks>
       </Docs>