refactor(upgrade): ensure compatibility with noImplicitOverride (#42512)

Adds the `override` keyword to the `upgrade` sources to ensure
compatibility with `noImplicitOverride`.

PR Close #42512

packages/upgrade/src/common/src/downgrade_component.ts

@@ -232,7 +232,7 @@ class ParentInjectorPromise extends SyncPromise<Injector> {
     element.data!(this.injectorKey, this);
   }
 
-  resolve(injector: Injector): void {
+  override resolve(injector: Injector): void {
     // Store the real injector on the element.
     this.element.data!(this.injectorKey, injector);