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/forms/src/directives/radio_control_value_accessor.ts

@@ -9,7 +9,6 @@
 import {Directive, ElementRef, Injectable, Injector, Input, OnDestroy, OnInit, Renderer, forwardRef} from '@angular/core';
 
 import {ListWrapper} from '../facade/collection';
-import {isPresent} from '../facade/lang';
 
 import {ControlValueAccessor, NG_VALUE_ACCESSOR} from './control_value_accessor';
 import {NgControl} from './ng_control';