[GTK4] update to 4.12.5

[jwahlstrand]

The recent gdk_pixbuf_jll update broke GTK4_jll on many platforms when newer Libtiff versions are used (https://github.com/JuliaGtk/Gtk4.jl/actions/runs/7686075699). For example:

Failed to precompile Gtk4 [9db2cae5-386f-4011-9d63-a5602296539b] to "/home/runner/.julia/compiled/v1.10/Gtk4/jl_FCduxn".
ERROR: LoadError: InitError: could not load library "/home/runner/.julia/artifacts/39e984f1f5ca7a704819f3b43a21e6aa7740c6ad/lib/libgtk-4.so"
libtiff.so.5: cannot open shared object file: No such file or directory

I noticed that libtiff is a dependency of GTK4 (not just via gdk_pixbuf) but was not explicitly listed, which I guess is why it was missed in JuliaRegistries/General#86099. I added a Libtiff dependency here with the same compat version as used in gdk_pixbuf_jll. If there's a more correct way to fix this let me know.

The compat of the old GTK4_jll versions should be fixed in the registry. Since there was no libtiff compat before, I was thinking of setting a gdk_pixbuf compat.