test: fix typings for DoneFn (#25163)

This also fixes CI tests, which were accidentally broken in #24663.

PR Close #25163

packages/core/test/bundling/hello_world_r2/treeshaking_spec.ts

@@ -6,7 +6,6 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
-import {withBody} from '@angular/core/testing';
 import * as fs from 'fs';
 import * as path from 'path';