CI: upgrade actions/checkout

Author: Wenzel

.github/workflows/ci.yml

@@ -13,7 +13,7 @@ jobs:
   lint:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
 
       - name: Set up Python 3.7 🐍
         uses: actions/setup-python@v1
@@ -33,7 +33,7 @@ jobs:
         python: ['3.7', '3.8', '3.9', '3.10', '3.11']
 
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
         with:
           path: python-libvmi