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/compiler/test/util_spec.ts

@@ -7,7 +7,7 @@
  */
 
 import {fakeAsync} from '@angular/core/testing/fake_async';
-import {beforeEach, beforeEachProviders, ddescribe, describe, expect, iit, inject, it, xit} from '@angular/core/testing/testing_internal';
+import {describe, expect, it} from '@angular/core/testing/testing_internal';
 
 import {SyncAsyncResult, splitAtColon} from '../src/util';