Revert unwanted change (#36807).

git-svn-id: https://svn.redmine.org/redmine/trunk@21595 e93f8b46-1217-0410-a6f0-8f06a7374b81

Author: marius-balteanu

Gemfile

@@ -41,7 +41,7 @@ end
 
 # Optional Markdown support, not for JRuby
 # ToDo: Remove common_mark group when common_mark is decoupled from markdown. See defect (#36892) for more details.
-gem 'redcarpet', '~> 3.5.1', groups: [:markdown]
+gem 'redcarpet', '~> 3.5.1', groups: [:markdown, :common_mark]
 
 # Optional CommonMark support, not for JRuby
 group :common_mark do