tests: Do not use gnome.genmarshal()
tests: Do not use gnome.genmarshal()

We are providing glib-genmarshal; using the gnome module in Meson does
not call the just built glib-genmarshal tool.

johne53/MB3Glib,endlessm/glib,endlessm/glib,endlessm/glib,johne53/MB3Glib,johne53/MB3Glib,johne53/MB3Glib,johne53/MB3Glib,endlessm/glib,endlessm/glib,johne53/MB3Glib