Test with Ruby 3.3

Author: eduardoj

.github/workflows/spec.yml

@@ -11,7 +11,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        ruby: [ '3.1', '3.2', 'head' ]
+        ruby: [ '3.1', '3.2', '3.3', 'head' ]
         rails: [ 'gemfiles/Gemfile.rails-6.1.x', 'gemfiles/Gemfile.rails-7.0.x', 'gemfiles/Gemfile.rails-7.1.x']
         exclude: []
     continue-on-error: ${{ endsWith(matrix.ruby, 'head') || matrix.ruby == 'debug' }}