stick to checkout v2

.github/workflows/main.yml

@@ -25,7 +25,7 @@ jobs:
     # Steps represent a sequence of tasks that will be executed as part of the job
     steps:
       # Checks-out your repository under $GITHUB_WORKSPACE, so your job can access it
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v2
         with:
           fetch-depth: 0