Bring CE-EE parity to app/services/projects/destroy_service.rb

Part of https://gitlab.com/gitlab-org/gitlab-ee/issues/6047

EE diff after:

diff --git a/app/services/projects/destroy_service.rb b/app/services/projects/destroy_service.rb
index 077d27c5836..2f8484976c2 100644
--- a/app/services/projects/destroy_service.rb
+++ b/app/services/projects/destroy_service.rb
@@ -1,6 +1,7 @@
 module Projects
   class DestroyService < BaseService
     include Gitlab::ShellAdapter
+    prepend ::EE::Projects::DestroyService
 
     DestroyError = Class.new(StandardError)