Dedupe server error notifications

Summary:
These notifications, when emit, don't get deduped, so if connection timeouts keep happening, like in [this](https://fb.workplace.com/groups/flippersupport/posts/1257144721432850), then you get tons of notifications.

This dedupes them if all the info is the same.

Reviewed By: mweststrate

Differential Revision: D32560073

fbshipit-source-id: beb4d67e2a97841bb91add7847157176dee4a5f4

desktop/flipper-ui-core/src/dispatcher/flipperServer.tsx

@@ -46,12 +46,14 @@ export default async (store: Store, logger: Logger) => {
   });
 
   server.on('notification', ({type, title, description}) => {
-    console.warn(`[$type] ${title}: ${description}`);
+    const text = `[$type] ${title}: ${description}`;
+    console.warn(text);
     notification.open({
       message: title,
       description: description,
       type: type,
       duration: 0,
+      key: text,
     });
   });