ci: drop rubies that are out of upstream support

Author: flavorjones

.github/workflows/ci.yml

@@ -20,14 +20,13 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        ruby: ["2.7", "3.0", "3.1", "3.2", "3.3", "head"]
+        ruby: ["3.1", "3.2", "3.3", "head"]
     steps:
       - uses: actions/checkout@v4
       - run: rm Gemfile.lock
       - uses: ruby/setup-ruby@v1
         with:
           ruby-version: ${{matrix.ruby}}
-          rubygems: "3.4.22" # last version to support Ruby 2.7
           bundler: latest
           bundler-cache: true
       - name: Run tests