update CI checkout to v4

Author: QuentinGruber

.github/workflows/ci.yml

@@ -44,7 +44,7 @@ jobs:
     name: Stylua
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
       - run: date +%W > weekly
 
       - name: Restore cache
@@ -65,7 +65,7 @@ jobs:
     name: Luacheck
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
       - name: Setup
         run: |
           sudo apt-get update