main/gtk+3.0: add patch to track serials
The patch[1] has been upstream for a long while. There seems to be no blocker, but more like GTK3 is on very low maintenance work. Having this patch is a requirement for Phosh, and would allow postmarketOS to drop our own fork
[1] https://gitlab.gnome.org/GNOME/gtk/-/merge_requests/5628