Test with Ruby 4.0 on CI

Author: ankane

.github/workflows/build.yml

@@ -13,7 +13,7 @@ jobs:
       - uses: actions/checkout@v5
       - uses: ruby/setup-ruby@v1
         with:
-          ruby-version: 3.4
+          ruby-version: "4.0"
           bundler-cache: true
       - if: ${{ startsWith(matrix.os, 'macos') }}
         run: brew install libomp