community/postmarketos-ondev: move from testing, upgrade to 0.4.2

Move postmarketos-ondev to community, along with dependencies. Upgrade to the latest postmarketos-ondev version, which only contains an important compatibility fix against calamares-extensions 1.1.1 (without it, resulting installations won't find the rootfs).

@PureTryOut: FYI: I took over maintenance of qtvirtualkeyboard-plasma.

@uuser: I've moved unclutter-xfixes, which you maintain, from testing to community. It has been in testing since 2017 and the package works fine, I think moving it is appropriate. If you don't want to maintain the package in community, I could also take over maintenance.