Fix typo in assertion method

[leobossmann]

Description of change

This pull request updates the unit tests in tests/unittests/test_date_window.py. The change replaces the deprecated assertEquals method with the correct assertEqual method in several test cases.

• Testing improvements:
  • Replaced all instances of self.assertEquals with self.assertEqual in the test_date_window.py unit tests.

QA steps

• manual qa steps passing (list below)
  coverage run -m pytest tests/unittests passes without error

Risks

None that I am aware of

Rollback steps

• revert this branch