chore(test): remove deprecated RootTestComponent

Uses of `RootTestComponent` should be migrated to `ComponentFixture`.

modules/angular2/src/testing/test_component_builder.ts

@@ -24,9 +24,9 @@ import {DebugElement, DebugElement_} from 'angular2/src/core/debug/debug_element
 
 
 /**
- * @deprecated Use ComponentFixture
+ * Fixture for debugging and testing a component.
  */
-export abstract class RootTestComponent {
+export abstract class ComponentFixture {
   debugElement: DebugElement;
 
   abstract detectChanges(): void;
@@ -34,9 +34,6 @@ export abstract class RootTestComponent {
 }
 
 
-export abstract class ComponentFixture extends RootTestComponent {}
-
-
 export class ComponentFixture_ extends ComponentFixture {
   /** @internal */
   _componentRef: ComponentRef;