CI: don't pin a ruby version

Author: nicolaiarocci

.github/workflows/release.yml

@@ -36,7 +36,7 @@ jobs:
       - name: Set up Ruby
         uses: ruby/setup-ruby@v1
         with:
-          ruby-version: '3.0.0'
+          ruby-version: ruby
           bundler-cache: true
 
       - name: Publish to RubyGems