Not clearing up a previous client connection should not log as error

Summary:
^
This doesn't seem a functionality impairment and there's no actionable items.

Reviewed By: lawrencelomax

Differential Revision: D34787962

fbshipit-source-id: 9fe42187456bfab3748d469860f6ed7cda2f83d5

desktop/flipper-ui-core/src/reducers/connections.tsx

@@ -306,7 +306,7 @@ export default (state: State = INITAL_STATE, action: Actions): State => {
 
       return produce(state, (draft) => {
         if (draft.clients.has(payload.id)) {
-          console.error(
+          console.warn(
             `Received a new connection for client ${payload.id}, but the old connection was not cleaned up`,
           );
         }