[gtk] Non-fast-forward update to branch wip/chergert/fix-4625

[Christian Hergert <chergert src gnome org>]

The branch 'wip/chergert/fix-4625' was changed in a way that was not a fast-forward update.
NOTE: This may cause problems for people pulling from the branch. For more information,
please see:

 https://wiki.gnome.org/Git/Help/NonFastForward

Commits removed from the branch:

  2505ff5... gsk/gl: use critical instead of assert for unrealize check

Commits added to the branch:

  654d74b... gsk/gl: use critical instead of assert in dispose