test(notifications): ✅ Update assertion to verify push channel notification call count

Co-Authored-By: Lilith Autocommit <noreply@atlilith.com>

messenger/notifications/backend/__tests__/push.channel.spec.ts

@@ -59,7 +59,7 @@ describe('PushChannel', () => {
       const reminder = makeReminder();
       await channel.dispatch(reminder);
 
-      expect(mockFetch).toHaveBeenCalledOnce();
+      expect(mockFetch).toHaveBeenCalledTimes(1);
       const [url, init] = mockFetch.mock.calls[0] as [string, RequestInit];
       expect(url).toBe('http://localhost:3850/api/push/fire');
       expect(init.method).toBe('POST');