Move EE code out of HookData::IssueBuilder

This ensures that Gitlab::HookData::IssueBuilder uses the same code in
CE and EE.

lib/gitlab/hook_data/issue_builder.rb

@@ -3,8 +3,6 @@
 module Gitlab
   module HookData
     class IssueBuilder < BaseBuilder
-      prepend ::EE::Gitlab::HookData::IssueBuilder # rubocop: disable Cop/InjectEnterpriseEditionModule
-
       SAFE_HOOK_RELATIONS = %i[
         assignees
         labels
@@ -55,3 +53,5 @@ module Gitlab
     end
   end
 end
+
+Gitlab::HookData::IssueBuilder.prepend(EE::Gitlab::HookData::IssueBuilder)