Bump GitLab CI YML Ruby version

.gitlab-ci.yml

-image: ruby:2.6
+image: ruby:2.7
 
 cache:
   paths:
@@ -15,6 +15,7 @@ test:
   - export GEM_HOME=$PWD/gems
   - export PATH=$PWD/gems/bin:$PATH
   - gem install bundler
+  - gem install activesupport -v 6.1.7
   - gem install bridgetown -N
   - bundle install
   - yarn install