Update actions/checkout action to v6

Author: renovate[bot]

.github/workflows/lint.yaml

@@ -14,7 +14,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Check out repository
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
       - name: Set up python
         id: setup-python
         uses: actions/setup-python@v6

.github/workflows/pypi-publish.yaml

@@ -7,7 +7,7 @@ jobs:
   publish:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
 
       - name: Set up Python
         uses: actions/setup-python@v6