update tests to test fetching all Git commits

Co-authored-by: Alexander Streed <[email protected]>

tests/test_repositories.py

@@ -155,7 +155,7 @@ class p:
         mock = AsyncMock(return_value=p())
         monkeypatch.setattr(prefect_gitlab.repositories, "run_process", mock)
         repo = "[email protected]:PrefectHQ/prefect.git"
-        depth = 0
+        depth = None
         g = GitLabRepository(
             repository=repo,
             git_depth=depth,