Remove unused operations/helper

ee/spec/frontend/operations/helpers.js

-/**
- * @deprecated
- * DO NOT USE! This causes issues when `vue-test-utils` is used elsewhere.
- * This function will be removed in https://gitlab.com/gitlab-org/gitlab/issues/9594.
- */
-export function getChildInstances(vm, WrappedComponent) {
-  return vm.$children.filter(child => child instanceof WrappedComponent);
-}
-
-export function mouseEvent(el, eventType) {
-  const event = document.createEvent('MouseEvent');
-  event.initMouseEvent(eventType);
-  el.dispatchEvent(event);
-}