CI: Don't use custom image

.gitlab-ci.yml

@@ -67,7 +67,10 @@ extension:
     - job: lint
       optional: true
     - reuse
-  image: registry.gitlab.com/rmnvgr/nightthemeswitcher-gnome-shell-extension:latest
+  image: debian:stable-slim
+  before_script:
+    - apt update
+    - apt install --no-install-recommends -y gettext libglib2.0-bin libglib2.0-dev-bin meson zip
   script:
     - meson builddir -Dpack=true -Dpackdir=.
     - meson install -C builddir
@@ -132,7 +135,10 @@ release:
 pages:
   stage: deploy
   needs: []
-  image: registry.gitlab.com/rmnvgr/nightthemeswitcher-gnome-shell-extension:latest
+  image: debian:stable-slim
+  before_script:
+    - apt update
+    - apt install --no-install-recommends -y gzip brotli
   script:
     - cp -r website public
     - find public -type f -regex '.*\.\(|html\|css\|svg\|png\|woff\|woff2\)$' -exec gzip -f -k {} \;