chore(deps): update docker/login-action action to v4

Signed-off-by: milkmaker <milkmaker@mailcow.de>

.github/workflows/rebuild_backup_image.yml

@@ -23,7 +23,7 @@ jobs:
 
       - name: Login to GHCR
         if: github.event_name != 'pull_request'
-        uses: docker/login-action@v3
+        uses: docker/login-action@v4
         with:
           registry: ghcr.io
           username: ${{ github.repository_owner }}