CI pytest-commits should only test changed ui packages

CI can fail in MRs because of upstream/unrelated issues, when it is running the test_ui pytest. It should only test UI packages if the UI package was changed in the MR.

Context:

CI has been broken pretty much all day (March 10th US time) because the plasma mobile UI in pmaports depends on angelfish, and plamo also supports armv7, but there is no armv7 build of angelfish in aports:

FAILED .ci/testcases/test_ui.py::test_aports_ui - RuntimeError: /builds/postmarketOS/pmaports/main/postmarketos-ui-plasma-mobile/APKBUILD: package 'angelfish' from _pmb_recommends not found for arch 'armv7'