Do not post entire Wiki page content as chat notification

What does this MR do?

See #20812 (closed)

Screenshots

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.

app/models/project_services/chat_message/wiki_page_message.rb

@@ -14,7 +14,7 @@ def initialize(params)
       obj_attr = HashWithIndifferentAccess.new(obj_attr)
       @title = obj_attr[:title]
       @wiki_page_url = obj_attr[:url]
-      @description = obj_attr[:content]
+      @description = obj_attr[:message]
 
       @action =
         case obj_attr[:action]