chore(deps): update actions/checkout action to v4

Author: renovate-bot

.github/workflows/lint.yml

@@ -29,7 +29,7 @@ jobs:
         run: pip install nox
 
       - name: Checkout code
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
 
       - name: Run nox lint session
         run: nox --sessions lint

.github/workflows/run_tests.yml

@@ -26,7 +26,7 @@ jobs:
 
     steps:
       # check out repository
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
 
       - name: Set up Python 3.9
         uses: actions/setup-python@v4