Revert "refactor: optimize plugins for angular treeshaking"

This reverts commit 8b53c04dc5.

src/@ionic-native/plugins/admob-plus/index.ts

@@ -72,9 +72,7 @@ export class RewardVideo {
     pluginRef: 'admob',
     repo: 'https://github.com/admob-plus/admob-plus',
 })
-@Injectable({
-  providedIn: 'root'
-})
+@Injectable()
 export class AdMob extends IonicNativePlugin {
     banner = new Banner();
     interstitial = new Interstitial();