main/postmarketos-ui-lxqt: fix dep: lxpolkit -> lxqt-policykit
lxpolkit has been removed in Alpine, adjust our packaging:
this is dead for 10 years, pretty much superceded by lxqt-policykit
Related: https://gitlab.alpinelinux.org/alpine/aports/-/commit/9df419c349175cda0e635ec2bae13683b7eb916f