Update GitHub Actions to use rubies >= 3.0.

Author: hainesr

.github/workflows/lint.yml

@@ -12,7 +12,7 @@ jobs:
     - name: Install and set up ruby
       uses: ruby/setup-ruby@v1
       with:
-        ruby-version: 2.4
+        ruby-version: '3.0'
         bundler-cache: true
 
     - name: Rubocop

.github/workflows/tests.yml

@@ -8,12 +8,12 @@ jobs:
       fail-fast: false
       matrix:
         os: [ubuntu]
-        ruby: ['2.4', '2.5', '2.6', '2.7', '3.0', '3.1', '3.2', '3.3', '3.4', head, jruby, jruby-head, truffleruby, truffleruby-head]
+        ruby: ['3.0', '3.1', '3.2', '3.3', '3.4', head, jruby, jruby-head, truffleruby, truffleruby-head]
         include:
           - os: macos
-            ruby: '2.6'
+            ruby: '3.0'
           - os: windows
-            ruby: '2.4.10'
+            ruby: '3.0'
     runs-on: ${{ matrix.os }}-latest
     continue-on-error: ${{ endsWith(matrix.ruby, 'head') || matrix.os == 'windows' }}
     steps: