refactor(core): Removes unused flag for onDestroy

Eliminates an unnecessary configuration flag

packages/core/src/linker/destroy_ref.ts

@@ -12,8 +12,6 @@ import {LView} from '../render3/interfaces/view';
 import {getLView} from '../render3/state';
 import {removeLViewOnDestroy, storeLViewOnDestroy} from '../render3/util/view_utils';
 
-const EXECUTE_CALLBACK_IF_ALREADY_DESTROYED = false;
-
 /**
  * `DestroyRef` lets you set callbacks to run for any cleanup or destruction behavior.
  * The scope of this destruction depends on where `DestroyRef` is injected. If `DestroyRef`
@@ -84,12 +82,6 @@ export class NodeInjectorDestroyRef extends DestroyRef {
   override onDestroy(callback: () => void): () => void {
     const lView = this._lView;
 
-    // TODO(atscott): Remove once g3 cleanup is complete
-    if (EXECUTE_CALLBACK_IF_ALREADY_DESTROYED && isDestroyed(lView)) {
-      callback();
-      return () => {};
-    }
-
     storeLViewOnDestroy(lView, callback);
     return () => removeLViewOnDestroy(lView, callback);
   }