Gemmi Release Bug

[j-c-c]

Gemmi had a recent release that deprecates Gemmi.Loop.val in favor of __getitem__/__setitem__ (see here), causing CI to break: https://github.com/ComputationalCryoEM/ASPIRE-Python/actions/runs/7933088082/job/21742679882#step:6:587

[j-c-c]

closed by #1089