Renovate: Update actions/checkout action to v6

Author: renovate[bot]

.github/workflows/publish-helm.yml

@@ -20,7 +20,7 @@ jobs:
 
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: Install Helm
         uses: azure/setup-helm@v4.3.1