Split webkit2gtk-5.0 from webkitgtk.inc
webkitgtk.inc will need to move on to 2.40 soon so that GTK 3 applications can continue to receive security updates. GTK 4 applications, however, will be cut off due to the API change webkit2gtk-5.0 -> webkitgtk-6.0. GTK 4 applications should switch to the GNOME 44 runtime now.
This change is for the GNOME 43 runtime only. No other runtime versions require this change.