Adding missing param description to NetworkStream.Write(System.ReadOnlySpan{System.Byte}) (#2897)

After adding documentation for System.Net.Sockets in #2767, we found out that one param went away with no proper description.
This change adds the missing description to it.

Author: jozkee

xml/System.Net.Sockets/NetworkStream.xml

@@ -1902,7 +1902,7 @@ Call `Dispose` when you are finished using the <xref:System.Net.Sockets.NetworkS
         <Parameter Name="buffer" Type="System.ReadOnlySpan&lt;System.Byte&gt;" Index="0" FrameworkAlternate="netcore-3.0" />
       </Parameters>
       <Docs>
-        <param name="buffer">To be added.</param>
+        <param name="buffer">The data to write to the <see cref="T:System.Net.Sockets.NetworkStream" />.</param>
         <summary>Writes data to the <see cref="T:System.Net.Sockets.NetworkStream" />  from a read-only byte span.</summary>
         <remarks>
           <format type="text/markdown"><![CDATA[
@@ -2299,4 +2299,4 @@ There was a failure while writing to the network.</exception>
       </Docs>
     </Member>
   </Members>
-</Type>
+</Type>