Final polish: standardize YAML format to match repository conventions

Co-authored-by: BenjaminMichaelis <22186029+BenjaminMichaelis@users.noreply.github.com>

Author: Copilot

.github/workflows/sync-version-branches.yml

@@ -1,5 +1,5 @@
 name: Sync v12.0 -> v13.0
-'on':
+on:
   push:
     branches:
       - 'v12.0'
@@ -23,4 +23,4 @@ jobs:
           resolve_conflicts: "false"
           git_committer_name: 'BenjaminMichaelisBot'
           git_committer_email: 'github@relay.benjamin.michaelis.net'
-          github_token: ${{ secrets.GIT_PUSHTOKEN }}
+          github_token: ${{ secrets.GIT_PUSHTOKEN }}