ci: Rebase image to F42

Fedora has branched, and GNOME 48 updates have been landing;
this seems like a good moment to rebase our CI image.

Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/3676>

.gitlab-ci.yml

@@ -40,7 +40,7 @@ default:
   image: $MUTTER_CI_IMAGE
 
 variables:
-  MUTTER_CI_IMAGE: registry.gitlab.gnome.org/gnome/mutter/fedora/41:x86_64-2025-02-19.1
+  MUTTER_CI_IMAGE: registry.gitlab.gnome.org/gnome/mutter/fedora/42:x86_64-2025-03-31.0
   FDO_UPSTREAM_REPO: GNOME/gnome-shell
   BUNDLE: "extensions-git.flatpak"
   LINT_LOG: "eslint-report.xml"

.gitlab-ci/build-toolbox-image.sh

@@ -33,6 +33,7 @@ build_container() {
     flatpak-spawn # run host commands
     flatpak # for host apps
     nautilus # FileChooser portal
+    adwaita-fonts-all # system fonts
     gnome-backgrounds # no blank background!
   )
   local debug_packages=(
@@ -53,9 +54,6 @@ build_container() {
   local srcdir=$(realpath $(dirname $0))
   buildah copy --chmod 755 $build_cntr $srcdir/install-meson-project.sh /usr/libexec
 
-  buildah run $build_cntr /usr/libexec/install-meson-project.sh \
-    https://gitlab.gnome.org/GNOME/adwaita-fonts.git main
-
   # include convenience script for updating mutter dependency
   local update_mutter=$(mktemp)
   cat > $update_mutter <<-EOF