Fix blank error message for codequality diff

Pass createFlash an object instead of just the string

Changelog: fixed
EE: true

ee/app/assets/javascripts/diffs/store/actions.js

@@ -42,7 +42,9 @@ export const fetchCodequality = ({ commit, state, dispatch }) => {
       }
     },
     errorCallback: () =>
-      createFlash(__('Something went wrong on our end while loading the code quality diff.')),
+      createFlash({
+        message: __('Something went wrong on our end while loading the code quality diff.'),
+      }),
   });
 
   if (!Visibility.hidden()) {

ee/spec/frontend/diffs/store/actions_spec.js

@@ -63,7 +63,9 @@ describe('EE DiffsStoreActions', () => {
 
       testAction(fetchCodequality, {}, { endpoint }, [], [], () => {
         expect(createFlash).toHaveBeenCalledTimes(1);
-        expect(createFlash).toHaveBeenCalledWith(expect.stringMatching('Something went wrong'));
+        expect(createFlash).toHaveBeenCalledWith({
+          message: 'Something went wrong on our end while loading the code quality diff.',
+        });
         done();
       });
     });