test: move mockWarn into setup files

packages/runtime-dom/__tests__/helpers/useCssModule.spec.ts

@@ -1,10 +1,7 @@
 import { render, h, nodeOps } from '@vue/runtime-test'
 import { useCssModule } from '../../src/helpers/useCssModule'
-import { mockWarn } from '@vue/shared'
 
 describe('useCssModule', () => {
-  mockWarn()
-
   function mountWithModule(modules: any, name?: string) {
     let res
     render(

packages/runtime-dom/__tests__/patchProps.spec.ts

@@ -1,10 +1,7 @@
 import { patchProp } from '../src/patchProp'
 import { render, h } from '../src'
-import { mockWarn } from '@vue/shared'
 
 describe('runtime-dom: props patching', () => {
-  mockWarn()
-
   test('basic', () => {
     const el = document.createElement('div')
     patchProp(el, 'id', null, 'foo')