cleanup: mcclim-drei.asd: use :if-feature
cleanup: mcclim-drei.asd: use :if-feature

This is a good practice suggested by ASDF manual pointed out by Javier
Olaechea. Related commit 20bda1d9806e0001c328dc37dc43a6ea5e07171a.

onixie/mcclim,onixie/mcclim,slyrus/mcclim,slyrus/mcclim,onixie/mcclim