Use docker variant of OskarStark/php-cs-fixer-ga require

Author: emodric

.github/workflows/coding_standards.yml

@@ -21,6 +21,6 @@ jobs:
         with:
           repository: netgen-layouts/layouts-coding-standard
           path: vendor/netgen/layouts-coding-standard
-      - uses: OskarStark/php-cs-fixer-ga@master
+      - uses: docker://oskarstark/php-cs-fixer-ga
         with:
           args: --diff --dry-run