message: refactor(common): remove unused method in internal `SubscriptionStrategy` interface
  The `onDestroy` method was not being called so this commit removes it entirely.
  PR Close
diff: @@ -15,7 +15,6 @@ interface SubscriptionStrategy {
  createSubscription(async: Subscribable<any>|Promise<any>, updateLatestValue: any): Unsubscribable
  |Promise<any>;
  dispose(subscription: Unsubscribable|Promise<any>): void;
  - onDestroy(subscription: Unsubscribable|Promise<any>): void;
  }
  class SubscribableStrategy implements SubscriptionStrategy {
  @@ -31,10 +30,6 @@ class SubscribableStrategy implements SubscriptionStrategy {
  dispose(subscription: Unsubscribable): void {
  subscription.unsubscribe();
  }
  -
  - onDestroy(subscription: Unsubscribable): void {
  - subscription.unsubscribe();
  - }
  }
  class PromiseStrategy implements SubscriptionStrategy {
  @@ -45,8 +40,6 @@ class PromiseStrategy implements SubscriptionStrategy {
  }
  dispose(subscription: Promise<any>): void {}
  -
  - onDestroy(subscription: Promise<any>): void {}
  }
  const _promiseStrategy = new PromiseStrategy();
  