Fix test mock for commits() to return iterator

The test_username_lookup_case_insensitive test was failing because it mocked
repo_data.commits() to return a list, but the main function expects an iterator
that can be used with next(). Also added explicit owning_team=None to ensure
the test takes the original commit author code path for case-insensitive lookup.

Fixes TypeError: list object is not an iterator

Signed-off-by: Zack Koppert <zkoppert@github.com>

Author: zkoppert

test_case_insensitive_lookup.py

@@ -153,6 +153,7 @@ def test_username_lookup_case_insensitive(
         mock_env.gh_app_private_key_bytes = None
         mock_env.gh_app_enterprise_only = False
         mock_env.chunk_size = 100
+        mock_env.owning_team = None  # Force using original commit author path
         mock_get_env_vars.return_value = mock_env
 
         # Mock GitHub connection and repository
@@ -166,7 +167,7 @@ def test_username_lookup_case_insensitive(
         # Mock first commit with different case username
         mock_commit = MagicMock()
         mock_commit.author.login = "Jeffrey-Luszcz"  # Different case!
-        mock_repo.commits.return_value = [mock_commit]
+        mock_repo.commits.return_value = iter([mock_commit])
 
         # Mock contributors with different case
         mock_contributor = MagicMock()