Use DeleteDropWatch instead of Delete in test

Using the latter resulted in receiving extra OnDelete event callbacks. Using
DeleteDropWatch removed the flake.

Fixes #14138.

pkg/controller/framework/controller_test.go

@@ -133,7 +133,7 @@ func ExampleInformer() {
 		time.Millisecond*100,
 		framework.ResourceEventHandlerFuncs{
 			AddFunc: func(obj interface{}) {
-				source.Delete(obj.(runtime.Object))
+				source.DeleteDropWatch(obj.(runtime.Object))
 			},
 			DeleteFunc: func(obj interface{}) {
 				key, err := framework.DeletionHandlingMetaNamespaceKeyFunc(obj)
@@ -327,7 +327,7 @@ func TestUpdate(t *testing.T) {
 				if !allowedTransitions[pair{from, to}] {
 					t.Errorf("observed transition %q -> %q for %v", from, to, n.Name)
 				}
-				source.Delete(n)
+				source.DeleteDropWatch(n)
 			},
 			DeleteFunc: func(obj interface{}) {
 				testDoneWG.Done()