Revert "main: Register session with GDM on startup"

Revert "main: Register session with GDM on startup"

This depends on GDM changes that are not in this release.

This reverts commit 6457a1454a05bac8f7e172c17fbcb2b5baeae619.

Origin: upstream, 49.4, commit:ba60daead6a54ec02ed5aa2841e72cd5acb591cb
Bug: https://gitlab.gnome.org/GNOME/gnome-shell/-/issues/8983
Bug: https://gitlab.gnome.org/GNOME/mutter/-/issues/4572
Bug-Debian: https://bugs.debian.org/1125273
Bug-Debian: https://bugs.debian.org/1125275
Bug-Debian: https://bugs.debian.org/1125941
Bug-Debian: https://bugs.debian.org/1126174

Gbp-Pq: Name Revert-main-Register-session-with-GDM-on-startup.patch