sudden failure of GMX test_u_nk_* tests

[orbeckst]

Since ~2 weeks ago, tests test_gmx.py::test_u_nk_XXXXX are failing (see CI https://github.com/alchemistry/alchemlyb/actions/runs/12720916470 ).

See, for example, most recent https://github.com/alchemistry/alchemlyb/actions/runs/12961537065/job/36156921523 :

=========================== short test summary info ============================
FAILED src/alchemlyb/tests/parsing/test_gmx.py::test_u_nk_with_total_energy - AssertionError: 
Arrays are not almost equal to 4 decimals
 ACTUAL: 47611374979.46824
 DESIRED: 47611374980.34574
FAILED src/alchemlyb/tests/parsing/test_gmx.py::test_u_nk_with_potential_energy - AssertionError: 
Arrays are not almost equal to 2 decimals
 ACTUAL: 16674040406471.553
 DESIRED: 16674040406778.867
FAILED src/alchemlyb/tests/parsing/test_gmx.py::test_u_nk_without_energy - AssertionError: 
Arrays are not almost equal to 2 decimals
 ACTUAL: 20572986866779.01
 DESIRED: 20572986867158.184
=========== 3 failed, 469 passed, 188 warnings in 235.42s (0:03:55) ============

We need to find out the reason and then decide if something requires fixing or we need to adjust tests (and possibly increase dependency versions to maintain expected behavior).