build: remove unused rollup.config.js files (#28646)

Since we build and publish the individual packages
using Bazel and `build.sh` has been removed, we can
safely remove the `rollup.config.js` files which are no
longer needed because the `ng_package` bazel rule
automatically handles the rollup settings and globals.

PR Close #28646

packages/compiler/testing/rollup.config.js

@@ -1,29 +0,0 @@
-/**
- * @license
- * Copyright Google Inc. All Rights Reserved.
- *
- * Use of this source code is governed by an MIT-style license that can be
- * found in the LICENSE file at https://angular.io/license
- */
-
-const resolve = require('rollup-plugin-node-resolve');
-const sourcemaps = require('rollup-plugin-sourcemaps');
-
-const globals = {
-  '@angular/core': 'ng.core',
-  '@angular/core/testing': 'ng.core.testing',
-  '@angular/compiler': 'ng.compiler',
-  'rxjs': 'rxjs',
-};
-
-module.exports = {
-  entry: '../../../dist/packages-dist/compiler/fesm5/testing.js',
-  dest: '../../../dist/packages-dist/compiler/bundles/compiler-testing.umd.js',
-  format: 'umd',
-  exports: 'named',
-  amd: {id: '@angular/compiler/testing'},
-  moduleName: 'ng.compiler.testing',
-  plugins: [resolve(), sourcemaps()],
-  external: Object.keys(globals),
-  globals: globals
-};