Enable `assumeImmutableResults` on the Iterations

This commit solves https://gitlab.com/gitlab-org/gitlab/-/issues/338566
It enables `assumeImmutableResults` on the Iterations.

ee/app/assets/javascripts/iterations/index.js

@@ -17,13 +17,13 @@ const apolloProvider = new VueApollo({
     {},
     {
       batchMax: 1,
+      assumeImmutableResults: true,
     },
   ),
 });
 
 export function initIterationsList(namespaceType) {
   const el = document.querySelector('.js-iterations-list');
-
   return new Vue({
     el,
     apolloProvider,