Announce: flatpak 1.12.5

[Alexander Larsson]

Available at:
  https://github.com/flatpak/flatpak/releases/tag/1.12.5

$ sha256sum flatpak-1.12.5.tar.xz
1cb4a0b0b0c1bdffe644011ee8d17e437b4917c21d4384ec111b3f328206166c
flatpak-1.12.5.tar.xz

 * Fixed a case where temrporary data was sometimes left in
   /var/lib/flatpak/appstream, and we now detect such leftover data and
   remove it.
 * Fix regressions in `flatpak history` since 1.9.1
   - Don't display the appstream branch used internally
   - Don't display temporary repositories used internally
   - Warn instead of failing if other non-app, non-runtime refs are found
   - Don't set up an unnecessary polkit agent for `flatpak history`
   - Add test coverage
 * Don't propagate GStreamer-related environment variables into sandbox
 * Fix a typo in an error message
 * Fix incorrect year in NEWS for 1.12.4 release
 * Translation update: pl