set is loading in success mutation

app/assets/javascripts/ide/stores/modules/merge_requests/mutations.js

@@ -9,6 +9,7 @@ export default {
     state.isLoading = false;
   },
   [types.RECEIVE_MERGE_REQUESTS_SUCCESS](state, data) {
+    state.isLoading = false;
     state.mergeRequests = data.map(mergeRequest => ({
       id: mergeRequest.id,
       iid: mergeRequest.iid,