chore(autocomplete): remove unused startWith import (#4288)

Author: epelc

src/lib/autocomplete/autocomplete-trigger.ts

@@ -27,7 +27,6 @@ import {Subscription} from 'rxjs/Subscription';
 import 'rxjs/add/observable/merge';
 import 'rxjs/add/observable/fromEvent';
 import 'rxjs/add/operator/filter';
-import 'rxjs/add/operator/startWith';
 import 'rxjs/add/operator/switchMap';
 
 /**