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/src/view_compiler/constants.ts

@@ -9,7 +9,6 @@
 import {ChangeDetectionStrategy, ViewEncapsulation} from '@angular/core';
 
 import {CompileIdentifierMetadata} from '../compile_metadata';
-import {isBlank} from '../facade/lang';
 import {Identifiers, resolveEnumIdentifier, resolveIdentifier} from '../identifiers';
 import * as o from '../output/output_ast';