Test with Ruby 4.0 on CI

Author: ankane

.github/workflows/build.yml

@@ -7,6 +7,6 @@ jobs:
       - uses: actions/checkout@v5
       - uses: ruby/setup-ruby@v1
         with:
-          ruby-version: 3.4
+          ruby-version: "4.0"
           bundler-cache: true
       - run: bundle exec rake test