fix assertion: expect(fn1) not expect(fn1.mock)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Signed-off-by: Fredrik Adelöw <freben@spotify.com>

packages/backend-defaults/src/entrypoints/scheduler/lib/TaskWorker.test.ts

@@ -329,7 +329,7 @@ describe.each(databases.eachSupportedId())('TaskWorker, %s', databaseId => {
     await new Promise(resolve => setTimeout(resolve, 250));
     expect(fn1).toHaveBeenCalledTimes(0);
     await waitForExpect(() => {
-      expect(fn1.mock).toHaveBeenCalled();
+      expect(fn1).toHaveBeenCalled();
     });
 
     // Start a second worker and make sure it waits but the first worker still works along