minor fix

Author: dshukertjr

packages/realtime_client/lib/src/websocket/websocket.dart

@@ -1,3 +1,3 @@
 export 'websocket_stub.dart'
     if (dart.library.io) 'websocket_io.dart'
-    if (bool.fromEnvironment) 'websocket_web.dart';
+    if (dart.library.js_interop) 'websocket_web.dart';