Update actions/checkout action to v6

Author: renovate[bot]

.github/workflows/lint.yml

@@ -13,7 +13,7 @@ jobs:
     permissions:
       contents: read
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - name: Set up Python
         uses: actions/setup-python@v5
@@ -38,7 +38,7 @@ jobs:
     # Skip if the last commit was from github-actions[bot] to avoid infinite loops
     if: github.actor != 'github-actions[bot]'
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
         with:
           token: ${{ secrets.GITHUB_TOKEN }}
           ref: ${{ github.head_ref || github.ref }}