ci: remove deprecated jobs

The functionality of these jobs exists in the normal
build job now and they are no longer needed.

citemplates@544836ee
2 jobs for master in 11 minutes and 6 seconds (queued for 1 second)
Status Job ID Name Coverage
  Test
failed #837789
flatpak
flatpak

00:11:06

 
  Deploy
skipped #837790
nightly
 
Name Stage Failure
failed
flatpak Test
Running after_script
Uploading artifacts for failed job
Uploading artifacts...
gitg-git.flatpak: found 1 matching files

repo.tar: found 1 matching files

.flatpak-builder/build/gitg/_flatpak_build/meson-logs/meson-log.txt: found 1 matching files

.flatpak-builder/build/gitg/_flatpak_build/meson-logs/testlog.txt: found 1 matching files

Uploading artifacts to coordinator... ok
id=837789 responseStatus=201 Created token=mQ3eKbvz
ERROR: Job failed: exit code 1