net: qualify that SO_REUSEADDR is only set on Unix (#7533)

Author: lpraneis

tokio/src/net/tcp/listener.rs

@@ -75,7 +75,7 @@ impl TcpListener {
         /// the addresses succeed in creating a listener, the error returned from
         /// the last attempt (the last address) is returned.
         ///
-        /// This function sets the `SO_REUSEADDR` option on the socket.
+        /// This function sets the `SO_REUSEADDR` option on the socket on Unix.
         ///
         /// To configure the socket before binding, you can use the [`TcpSocket`]
         /// type.