SM: Prevent unmovable SM variants from moving (#62000)
SM: Prevent unmovable SM variants from moving (#62000)

Previously, a hostile statue could move it by bumping into it. It would
still be dusted, but this left open the possibility of supposedly
immobile engines moving, albeit slowly and expensively.
Jordie0608/tgstation,Bawhoppen/-tg-station,MicroWorldwide/SS13-TG-station,Bawhoppen/-tg-station,ShizCalev/tgstation,Razharas/-tg-station,Jordie0608/tgstation,ShizCalev/tgstation,Bawhoppen/-tg-station,Cruix/-tg-station,Cruix/-tg-station,CPTANT/-tg-station,MicroWorldwide/SS13-TG-station,Bawhoppen/-tg-station,Razharas/-tg-station,MicroWorldwide/SS13-TG-station,Razharas/-tg-station,tgstation/tgstation,tgstation/tgstation,ShizCalev/tgstation,Bawhoppen/-tg-station,ShizCalev/tgstation,tgstation/-tg-station,tgstation/tgstation,CPTANT/-tg-station,MicroWorldwide/SS13-TG-station,tgstation/tgstation,MicroWorldwide/SS13-TG-station,ShizCalev/tgstation,Razharas/-tg-station,Jordie0608/tgstation,CPTANT/-tg-station,Cruix/-tg-station,Cruix/-tg-station,Cruix/-tg-station,Bawhoppen/-tg-station,ShizCalev/tgstation,tgstation/-tg-station,Cruix/-tg-station,Cruix/-tg-station,ShizCalev/tgstation,Razharas/-tg-station,Jordie0608/tgstation,MicroWorldwide/SS13-TG-station,MicroWorldwide/SS13-TG-station,tgstation/tgstation,MicroWorldwide/SS13-TG-station,tgstation/-tg-station,CPTANT/-tg-station,tgstation/tgstation,ShizCalev/tgstation,Razharas/-tg-station,Razharas/-tg-station,CPTANT/-tg-station,Jordie0608/tgstation,tgstation/tgstation,CPTANT/-tg-station,Razharas/-tg-station,Jordie0608/tgstation,CPTANT/-tg-station,tgstation/-tg-station,Jordie0608/tgstation,Cruix/-tg-station,tgstation/tgstation,Jordie0608/tgstation,CPTANT/-tg-station,Bawhoppen/-tg-station,Bawhoppen/-tg-station