Revert "Use g_object_unref also for Gtk+2"
Revert "Use g_object_unref also for Gtk+2"

This reverts commit ecd4ea6300405147d9a5c4f5afb3f9f46272cd4a.

mate-desktop/libmatekbd,mate-desktop/libmatekbd,monsta/libmatekbd,monsta/libmatekbd