Fix typo in 'rocket_ws' README.

contrib/ws/README.md

@@ -24,7 +24,7 @@ This crate provides WebSocket support for Rocket via integration with Rocket's
       ```rust
       #[get("/echo")]
       fn echo_stream(ws: ws::WebSocket) -> ws::Stream!['static] {
-          ws::stream! { ws =>
+          ws::Stream! { ws =>
               for await message in ws {
                   yield message?;
               }