✅(backend) fix flaky test in user search api

Make sure the full is never John for the first user in order to make
sure we always have only 2 users (as the search is performed on both the
email and the full name).
    
Fixes #1765
    
Signed-off-by: Anto59290 <antonin59290@hotmail.com>

src/backend/core/tests/test_api_users.py

@@ -311,7 +311,7 @@ def test_api_users_list_query_short_queries():
     """
     Queries shorter than 5 characters should return an empty result set.
     """
-    user = factories.UserFactory(email="paul@example.com")
+    user = factories.UserFactory(email="paul@example.com", full_name="Paul")
     client = APIClient()
     client.force_login(user)