Update actions/checkout action to v4

Author: renovate[bot]

.github/workflows/ci.yml

@@ -8,7 +8,7 @@ jobs:
     runs-on: "ubuntu-latest"
 
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
     - uses: actions/setup-node@v3
       with:
         node-version: '14'