ci: Switch to mutter's docker image

Mutter's CI now also builds gnome-shell to ensure that a MR doesn't
break the shell. Its docker image has therefore been updated to contain
all our deps as well, so we don't need our own image anymore.

https://gitlab.gnome.org/GNOME/gnome-shell/merge_requests/546

.gitlab-ci.yml

@@ -40,7 +40,7 @@ js_check:
         when: on_failure
 
 build:
-    image: registry.gitlab.gnome.org/gnome/gnome-shell/master:v1
+    image: registry.gitlab.gnome.org/gnome/mutter/master:v1
     stage: build
     before_script:
         - .gitlab-ci/checkout-mutter.sh
@@ -58,7 +58,7 @@ build:
             - build
 
 test:
-    image: registry.gitlab.gnome.org/gnome/gnome-shell/master:v1
+    image: registry.gitlab.gnome.org/gnome/mutter/master:v1
     stage: test
     before_script:
         - ninja -C mutter/build install
@@ -72,7 +72,7 @@ test:
         when: on_failure
 
 test-pot:
-    image: registry.gitlab.gnome.org/gnome/gnome-shell/master:v1
+    image: registry.gitlab.gnome.org/gnome/mutter/master:v1
     stage: test
     before_script:
         - ninja -C mutter/build install

.gitlab-ci/Dockerfile

@@ -1,19 +0,0 @@
-FROM registry.gitlab.gnome.org/gnome/mutter/master:v1
-
-RUN dnf -y update && dnf -y upgrade && \
-    dnf install -y 'dnf-command(copr)' && \
-    dnf copr enable -y fmuellner/gnome-shell-ci && \
-    dnf builddep -y gnome-shell --setopt=install_weak_deps=False && \
-
-    # bt only exports HAVE_BLUETOOTH to js, rest are outdated build-requires
-    dnf remove -y gnome-bluetooth-libs-devel dbus-glib-devel \
-                  upower-devel python3-devel && \
-
-    # We'll build mutter ourselves
-    dnf remove -y --noautoremove mutter mutter-devel && \
-
-    # Needed for tests
-    dnf install -y '*/xvfb-run' gdm-lib accountsservice-libs && \
-
-    dnf clean all && \
-    rm -rf /var/cache/dnf