editors/gedit-plugins: remove no longer used zeitgeist dependency

the gedit zeitgeist integration is gone since 3.36.0:
https://gitlab.gnome.org/GNOME/gedit-plugins/-/commit/5953e917f3b90cb60d3037bc804d0dbcf4109c1a

PR: 251637
Reported by: Greg V <greg@unrelenting.technology>