Move class method to the right place

This class method was defined in the private scope of the class but this
is not working as expected for class methods. The method should be
public as it's used outside from this class.

app/models/service.rb

@@ -145,6 +145,10 @@ class Service < ApplicationRecord
     %w(commit push tag_push issue confidential_issue merge_request wiki_page)
   end
 
+  def self.event_description(event)
+    ServicesHelper.service_event_description(event)
+  end
+
   def self.find_or_create_templates
     create_nonexistent_templates
     for_template
@@ -399,10 +403,6 @@ class Service < ApplicationRecord
     end
   end
 
-  def self.event_description(event)
-    ServicesHelper.service_event_description(event)
-  end
-
   def valid_recipients?
     activated? && !importing?
   end