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/pipe_resolver_mock_spec.ts

@@ -7,9 +7,7 @@
  */
 
 import {Injector, Pipe} from '@angular/core';
-import {beforeEach, ddescribe, describe, expect, iit, inject, it} from '@angular/core/testing/testing_internal';
-
-import {isBlank, stringify} from '../src/facade/lang';
+import {beforeEach, describe, expect, inject, it} from '@angular/core/testing/testing_internal';
 import {MockPipeResolver} from '../testing/index';
 
 export function main() {