Remove unused fixture(s)

[mattwthompson]

I found this nice plugin while debugging some unforced errors in another project. Fortunately it looks like the toolkit isn't hanging onto too much dead code in this respect

$ git checkout 0.16.5 && pytest --dead-fixtures                                                 8:30:21  ☁  0.16.5 ☀
HEAD is now at f8110b56 Fix merge (#1943)

Hey there, I believe the following fixture(s) are not being used:
Fixture name: create_circular_handler_dependencies, location: openff/toolkit/_tests/test_forcefield.py:1262
Fixture name: alkethoh_forcefield, location: openff/toolkit/_tests/test_forcefield.py:771

1 error in 8.75s

alkethoh_forcefield is actually used in a few places, it seems like

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 93.74%. Comparing base (6aa989e) to head (c974c74).

Additional details and impacted files