Revert "refactor: optimize plugins for angular treeshaking"

This reverts commit 8b53c04dc5.

src/@ionic-native/plugins/calendar/index.ts

@@ -87,9 +87,7 @@ export interface NameOrOptions {
   repo: 'https://github.com/EddyVerbruggen/Calendar-PhoneGap-Plugin',
   platforms: ['Android', 'iOS']
 })
-@Injectable({
-  providedIn: 'root'
-})
+@Injectable()
 export class Calendar extends IonicNativePlugin {
   /**
    * This function checks if we have permission to read/write from/to the calendar.