Bump actions/checkout version

Author: rosston

.github/workflows/main.yml

@@ -11,7 +11,7 @@ jobs:
         ruby-version: ['3.0', '3.3']
 
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
       - uses: ruby/setup-ruby@v1
         with:
           ruby-version: ${{ matrix.ruby-version }}