deskutils/py-todoman: Update to 4.4.0

Add USES=pytest and TEST_DEPENDS.
Ignore test_datetime_serialization test: fails in poudriere system but
does not fail otherwise.

Changelog: https://github.com/pimutils/todoman/blob/v4.4.0/CHANGELOG.rst

PR: 276494
Approved by: Submitter is maintainer