Update to Malcontent 0.11.0

This is the GTK 4 port.

This MR does not contain a change reverting 3ca8190f because, last time I checked, libflatpak in GNOME OS still links to libsoup2.4; Initial Setup transitively links to libsoup3.

I built this locally, and it runs in bst shell (with some tweaks to the runtime environment), but I haven't tested it in a full OS build.

I can see the following warning in the build log:

[--:--:--][        ][ main:core-deps/malcontent.bst-0    ] WARNING [unaliased-url]: tar source at core-deps/malcontent.bst [line 4 column 2]: Use of unaliased source download URL: https://gitlab.freedesktop.org/pwithnall/malcontent/-/archive/0.11.0/malcontent-0.11.0.tar.gz

I do not know what the right way is to refer to this source tarball. In the past, malcontent releases have been uploaded to Philip's personal server. He is away from work at the moment; while Georges and I have write access to the Malcontent repo we do not have access to Philip's server.

Please let me know what the best approach is!