Replace localVue.set with setData

ee/spec/frontend/vue_mr_widget/components/states/mr_widget_ready_to_merge_spec.js

-import { shallowMount, createLocalVue } from '@vue/test-utils';
+import { shallowMount } from '@vue/test-utils';
 import { MERGE_DISABLED_TEXT_UNAPPROVED } from 'ee/vue_merge_request_widget/mixins/ready_to_merge';
 import MergeImmediatelyConfirmationDialog from 'ee/vue_merge_request_widget/components/merge_immediately_confirmation_dialog.vue';
 import ReadyToMerge from '~/vue_merge_request_widget/components/states/ready_to_merge.vue';
@@ -10,7 +10,6 @@ import {
 import { MERGE_DISABLED_TEXT } from '~/vue_merge_request_widget/mixins/ready_to_merge';
 
 describe('ReadyToMerge', () => {
-  const localVue = createLocalVue();
   let wrapper;
   let vm;
 
@@ -48,7 +47,6 @@ describe('ReadyToMerge', () => {
         mr: { ...mr, ...mrUpdates },
         service,
       },
-      localVue,
       stubs: {
         MergeImmediatelyConfirmationDialog,
       },
@@ -76,7 +74,7 @@ describe('ReadyToMerge', () => {
 
       it('should return "Merge in progress"', () => {
         factory();
-        localVue.set(vm, 'isMergingImmediately', true);
+        wrapper.setData({ isMergingImmediately: true });
 
         expect(vm.mergeButtonText).toEqual('Merge in progress');
       });