main/postmarketos-base-ui-gnome: fix polkit conflict, pt. 2
Move the polkit-elogind into depends= instead of pmb_recommends=, so packages depending on postmarketos-base-ui-gnome can build successfully again. The previous fix only helped for "pmbootstrap install", this fix will help for both cases.
Without this, e.g. postmarketos-base-ui-gnome-mobile fails to build: https://builds.sr.ht/~postmarketos/job/1384469