chore(deps): update actions/checkout action to v6

Author: renovate[bot]

.github/workflows/renovate-config-check.yaml

@@ -12,7 +12,7 @@ jobs:
   validate:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - name: Validate renovate.json
         run: npx --yes --package renovate -- renovate-config-validator

.github/workflows/test-and-release.yaml

@@ -15,7 +15,7 @@ jobs:
     runs-on: ubuntu-24.04
 
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
 
       - uses: actions/setup-node@v6
         with: