Update actions/checkout to v5

Author: sshaw

.github/workflows/main.yml

@@ -21,7 +21,7 @@ jobs:
         ruby: ['3.4', '3.3', '3.2', '3.1', '3.0', '2.7']
 
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v5
       - uses: ruby/setup-ruby@v1
         with:
           bundler-cache: true