Set assumeImmutableResults to true

ee/app/assets/javascripts/epic/new_epic_bundle.js

@@ -6,7 +6,12 @@ import EpicForm from './components/epic_form.vue';
 Vue.use(VueApollo);
 
 const apolloProvider = new VueApollo({
-  defaultClient: createDefaultClient(),
+  defaultClient: createDefaultClient(
+    {},
+    {
+      assumeImmutableResults: true,
+    },
+  ),
 });
 
 export function initEpicForm() {