Update actions/checkout action to v6

Author: renovate[bot]

.github/workflows/lint.yml

@@ -16,7 +16,7 @@ jobs:
 
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: Run Ruff (latest)
         uses: astral-sh/ruff-action@v3

.github/workflows/test.yml

@@ -20,7 +20,7 @@ jobs:
     runs-on: "ubuntu-latest"
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: Install uv and set python version
         uses: astral-sh/setup-uv@v7