ci: Move style-check to .pre phase

We want the style checks running at the start of the CI pipeline, no
need to have a specific phase for it.

.gitlab-ci.yml

@@ -1,5 +1,4 @@
 stages:
-  - analysis
   - build
   - docs
   - flatpak
@@ -28,7 +27,7 @@ variables:
 style-check-diff:
   extends: .only-default
   image: registry.gitlab.gnome.org/gnome/gtk/fedora:v14
-  stage: analysis
+  stage: .pre
   allow_failure: true
   script:
     - .gitlab-ci/run-style-check-diff.sh