Update (or drop) the Docker image used by Flatpak job

The gnome-runtime-images have been recently migrated to Quay. This is already reflected in the template.

Please note this MR has been created semi-automatically. If it doesn't make sense, feel free to close it.
2 jobs for barthalion/gnome-runtime-images-quay in 56 minutes and 21 seconds (queued for 38 minutes and 13 seconds)