Renovate: Update actions/checkout action to v6

Author: renovate[bot]

.github/workflows/publish-chart.yml

@@ -16,7 +16,7 @@ jobs:
 
     steps:
       - name: Checkout code
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: Set up Helm
         uses: azure/setup-helm@v4

.github/workflows/test-chart.yml

@@ -9,7 +9,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Clone the code
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: Setup Go
         uses: actions/setup-go@v6