Bump actions/checkout version

Author: rosston

.github/workflows/ruby.yml

@@ -22,7 +22,7 @@ jobs:
         ruby-version: ['2.7', '3.1']
 
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v4
     - name: Set up Ruby
       uses: ruby/setup-ruby@v1
       with: