renamed the mid filler icon state (#61293)
renamed the mid filler icon state (#61293)

The filled line decals /obj/effect/turf_decal/trimline/<color>/filled/mid_joiner had a mismatch between the code and the dmi. I've changed the dmi's entry from trimline_fill_mid to trimline_mid_fill to keep consistency with the existing naming conventions.

Fixes a very tiny inconsistency for mappers and allows them to fill in the middle of the filled line turf decals.
ShizCalev/tgstation,MicroWorldwide/SS13-TG-station,ShizCalev/tgstation,MicroWorldwide/SS13-TG-station,Bawhoppen/-tg-station,CPTANT/-tg-station,Bawhoppen/-tg-station,tgstation/tgstation,tgstation/-tg-station,Bawhoppen/-tg-station,CPTANT/-tg-station,tgstation/tgstation,Cruix/-tg-station,WJohn/-tg-station,Jordie0608/tgstation,ShizCalev/tgstation,Razharas/-tg-station,Cruix/-tg-station,ShizCalev/tgstation,WJohn/-tg-station,tgstation/tgstation,Cruix/-tg-station,Cruix/-tg-station,WJohn/-tg-station,Razharas/-tg-station,WJohn/-tg-station,Cruix/-tg-station,MicroWorldwide/SS13-TG-station,Razharas/-tg-station,Jordie0608/tgstation,Razharas/-tg-station,Bawhoppen/-tg-station,Bawhoppen/-tg-station,CPTANT/-tg-station,tgstation/-tg-station,Cruix/-tg-station,CPTANT/-tg-station,Razharas/-tg-station,WJohn/-tg-station,ShizCalev/tgstation,tgstation/tgstation,Bawhoppen/-tg-station,Jordie0608/tgstation,tgstation/tgstation,Razharas/-tg-station,Bawhoppen/-tg-station,Jordie0608/tgstation,Razharas/-tg-station,CPTANT/-tg-station,tgstation/tgstation,tgstation/tgstation,ShizCalev/tgstation,CPTANT/-tg-station,tgstation/tgstation,ShizCalev/tgstation,MicroWorldwide/SS13-TG-station,MicroWorldwide/SS13-TG-station,Cruix/-tg-station,CPTANT/-tg-station,CPTANT/-tg-station,Razharas/-tg-station,MicroWorldwide/SS13-TG-station,Jordie0608/tgstation,Jordie0608/tgstation,tgstation/-tg-station,WJohn/-tg-station,Jordie0608/tgstation,WJohn/-tg-station,Bawhoppen/-tg-station,MicroWorldwide/SS13-TG-station,Jordie0608/tgstation,tgstation/-tg-station,Cruix/-tg-station,ShizCalev/tgstation,MicroWorldwide/SS13-TG-station