test(aio): move reflect-metadata polyfills to test.ts (#23234)

This resolves https://github.com/angular/angular-cli/issues/10333 and nicely cleans up the code.

PR Close #23234

aio/src/polyfills.ts

@@ -27,9 +27,6 @@
  * and executed before the rest of the application files are executed.
  */
 
-/** HACK: force import of environment.ts/environment.prod.ts to load env specific polyfills */
-import './environments/environment';
-
 /** ALL Firefox browsers require the following to support `@angular/animation`. **/
 // import 'web-animations-js';  // Run `npm install --save web-animations-js`.