Update checkout version

Author: xuanxu

.github/workflows/ci.yml

@@ -26,7 +26,7 @@ jobs:
       BUNDLE_GEMFILE: ${{ matrix.gemfile }}
 
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
 
       - name: Remove Gemfile lock
         run: |