chore(lint): remove unused imports (#11923)

This was done automatically by tslint, which can now fix issues it finds.
The fixer is still pending in PR https://github.com/palantir/tslint/pull/1568
Also I have a local bugfix for https://github.com/palantir/tslint/issues/1569
which causes too many imports to be deleted.

modules/@angular/platform-browser/testing/browser_util.ts

@@ -9,7 +9,7 @@
 import {NgZone} from '@angular/core';
 
 import {ListWrapper} from './facade/collection';
-import {RegExp, StringWrapper, global, isPresent, isString} from './facade/lang';
+import {StringWrapper, global, isPresent, isString} from './facade/lang';
 import {getDOM} from './private_import_platform-browser';
 
 export class BrowserDetection {