fix(packages): use ES modules for primary build (#11120)

modules/@angular/common/testing/location_mock.ts

@@ -6,11 +6,9 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
+import {Location, LocationStrategy} from '@angular/common';
 import {EventEmitter, Injectable} from '@angular/core';
 
-import {Location} from '../index';
-import {LocationStrategy} from '../src/location/location_strategy';
-
 
 /**
  * A spy for {@link Location} that allows tests to fire simulated location events.