ci: Update GitHub Actions

https://github.com/actions/checkout

Author: DimitriPapadopoulos

.github/workflows/ci.yaml

@@ -17,7 +17,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
       - name: Set up Python
         uses: actions/setup-python@v4
       - run:
@@ -44,7 +44,7 @@ jobs:
           - '3.11'
     steps:
       - name: Checkout
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
       - name: Set up Python ${{ matrix.python-version }}
         uses: actions/setup-python@v4
         with: