Update actions/checkout action to v4 (#1819)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

.github/workflows/test_python.yml

@@ -48,7 +48,7 @@ jobs:
   Documentation:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v4
     - name: Requirements
       run: pip install -U sphinx
     - name: Check links