refactor(elements): remove unused imports and properties (#36114)

- Remove imports that are not used.
- Remove private class properties that are not used outside of the
  constructor.

PR Close #36114

packages/elements/src/component-factory-strategy.ts

@@ -26,7 +26,7 @@ const DESTROY_DELAY = 10;
 export class ComponentNgElementStrategyFactory implements NgElementStrategyFactory {
   componentFactory: ComponentFactory<any>;
 
-  constructor(private component: Type<any>, private injector: Injector) {
+  constructor(component: Type<any>, injector: Injector) {
     this.componentFactory =
         injector.get(ComponentFactoryResolver).resolveComponentFactory(component);
   }

packages/elements/src/element-strategy.ts

@@ -5,7 +5,7 @@
  * Use of this source code is governed by an MIT-style license that can be
  * found in the LICENSE file at https://angular.io/license
  */
-import {ComponentFactory, Injector} from '@angular/core';
+import {Injector} from '@angular/core';
 import {Observable} from 'rxjs';
 
 /**