Updating fixup.yml workflow from template

Signed-off-by: Nextcloud bot <bot@nextcloud.com>

.github/workflows/fixup.yml

@@ -1,12 +1,20 @@
+# This workflow is provided via the organization template repository
+#
+# https://github.com/nextcloud/.github
+# https://docs.github.com/en/actions/learn-github-actions/sharing-workflows-with-your-organization
+
 name: Pull request checks
+
 on: pull_request
 
 jobs:
   commit-message-check:
     name: Block fixup and squash commits
+
     runs-on: ubuntu-latest
+
     steps:
       - name: Run check
-        uses: xt0rted/block-autosquash-commits-action@main
+        uses: xt0rted/block-autosquash-commits-action@v2
         with:
           repo-token: ${{ secrets.GITHUB_TOKEN }}