⬆️ upgrade actions/checkout action to v6

Author: renovate[bot]

.github/workflows/ci.yml

@@ -14,7 +14,7 @@ jobs:
 
     steps:
       - name: Checkout repo
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
         with:
           fetch-depth: 2
           token: ${{ secrets.GITHUB_TOKEN }}