Automatic port of CryptoStream docs (dotnet#4888)

Co-authored-by: carlossanlop <[email protected]>

Author: carlossanlop

xml/System.Security.Cryptography/CryptoStream.xml

@@ -880,9 +880,9 @@
         <Parameter Name="cancellationToken" Type="System.Threading.CancellationToken" Index="0" FrameworkAlternate="net-5.0" />
       </Parameters>
       <Docs>
-        <param name="cancellationToken">To be added.</param>
-        <summary>To be added.</summary>
-        <returns>To be added.</returns>
+        <param name="cancellationToken">The token to monitor for cancellation requests. The default value is <see cref="P:System.Threading.CancellationToken.None" />.</param>
+        <summary>Asynchronously updates the underlying data source or repository with the current state of the buffer, then clears the buffer.</summary>
+        <returns>A task that represents the asynchronous flush operation.</returns>
         <remarks>To be added.</remarks>
       </Docs>
     </Member>