Update DCFreeHedron.cpp
Update DCFreeHedron.cpp

Fix correction term calculation for branch molecules.
GOMC-WSU/GOMC,GOMC-WSU/GOMC,GOMC-WSU/GOMC,GOMC-WSU/GOMC,GOMC-WSU/GOMC_Serial,GOMC-WSU/GOMC_Serial,GOMC-WSU/GOMC,GOMC-WSU/GOMC_Serial