Update actions/checkout action to v7

Author: renovate[bot]

.github/workflows/pull_request.yaml

@@ -16,7 +16,7 @@ jobs:
     name: Python lint
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v7
         with:
           fetch-depth: 0
       - uses: actions/setup-python@v5