main/postmarketos-ui-phosh: remove systemd subpkg (MR 5743)

v24.06 doesn't have systemd, and this -systemd subpackage cannot be
installed because there is no phosh-service (as listed in depends="").
Fix it so the upstream-compat job doesn't complain about it anymore:

  Increase 'postmarketos-ui-phosh' pkgrel (6 -> 7), missing depend(s): phosh-service
[ci:skip-build]: already built successfully in CI