Run rubocop with ruby 3.0

(cherry picked from commit 8fb29ee)

Author: adamruzicka

.github/workflows/ruby_tests.yml

@@ -13,6 +13,7 @@ jobs:
     uses: theforeman/actions/.github/workflows/rubocop.yml@v0
     with:
       command: bundle exec rubocop --parallel --format github
+      ruby: 3.0
 
   test:
     name: Ruby