Drop support for ruby <3

Author: adamruzicka

.github/workflows/ruby.yml

@@ -19,15 +19,16 @@ jobs:
       ruby_version: ${{ steps.ruby_version.outputs.versions }}
     steps:
       - uses: actions/checkout@v5
+      - id: ruby_version
+        uses: voxpupuli/ruby-version@v1
       - name: Setup Ruby
         uses: ruby/setup-ruby@v1
         with:
-          ruby-version: 2.7
+          # The output is a list of ruby versions in descending order
+          ruby-version: ${{ fromJSON(steps.ruby_version.outputs.versions)[fromJSON(steps.ruby_version.outputs.versions).length - 1] }}
           bundler-cache: true
       - name: Run rubocop
         run: bundle exec rubocop
-      - id: ruby_version
-        uses: voxpupuli/ruby-version@v1
 
   test:
     runs-on: ubuntu-latest

dynflow.gemspec

@@ -18,7 +18,7 @@ Gem::Specification.new do |s|
   s.test_files    = `git ls-files -- {test,spec,features}/*`.split("\n")
   s.require_paths = ["lib"]
 
-  s.required_ruby_version = '>= 2.7.0'
+  s.required_ruby_version = '>= 3.0.0'
 
   s.add_dependency "algebrick", '~> 0.7.0'
   s.add_dependency "concurrent-ruby", '~> 1.1.3'