ci: Update Dockerfile to :v2

This commit is a bit deceitful: The main change in the image is not the more recent Fedora base, but an updated (and not backward-compatible) evolution-data-server package from the fmuellner/gnome-shell-ci copr.

gnome-shell!501 (merged) ports gnome-shell to the new API, so to keep mutter and gnome-shell CI working after that change, we need to build against the correct EDS version.