Run CI against more recent ruby versions (#34)

.github/workflows/actions.yml

@@ -1,29 +1,24 @@
 name: CI
 on: [push, pull_request]
-
 jobs:
   main:
     name: Ruby ${{ matrix.ruby }}
     runs-on: ubuntu-latest
     strategy:
       matrix:
         ruby:
-          - 2.5
-          - 2.6
           - 2.7
           - 3.0
+          - 3.1
+          - 3.2
     steps:
       - uses: actions/checkout@v4
-
       - uses: ruby/setup-ruby@v1
         with:
           ruby-version: ${{ matrix.ruby }}
-
       - name: Install gems
         run: bundle install
-
       - name: RuboCop
         run: bundle exec rubocop --parallel
-
       - name: RSpec
         run: bundle exec rspec