Remove useless variables in 'ErrorCrit_NSE'

The following command lines, usefull for 'ErrorCrit_KGE' and 'ErrorCrit_KGE2', are useless in 'ErrorCrit_NSE' and have to be removed, because the meanVarObs and meanVarSim objects are note used in the function.

## Other variables preparation
meanVarObs <- mean(EC$VarObs[!EC$TS_ignore])
meanVarSim <- mean(EC$VarSim[!EC$TS_ignore])