Fix ${VAR} formatting in :help :set_env.
Fix ${VAR} formatting in :help :set_env.

Kjwon15/dactyl,5digits/dactyl,moonshadow/dactyl,moonshadow/dactyl,nathyong/dactyl,invl/dactyl,nathyong/dactyl,nathyong/dactyl,madand/pentadactyl-pm,5digits/dactyl,invl/dactyl,airodactyl/dactyl,madand/pentadactyl-pm,Kjwon15/dactyl,madand/pentadactyl-pm,airodactyl/dactyl,invl/dactyl,Kjwon15/dactyl,madand/pentadactyl-pm,5digits/dactyl,nathyong/dactyl,Kjwon15/dactyl,airodactyl/dactyl,invl/dactyl,invl/dactyl,nathyong/dactyl,5digits/dactyl,madand/pentadactyl-pm,airodactyl/dactyl,5digits/dactyl,moonshadow/dactyl,airodactyl/dactyl,Kjwon15/dactyl,5digits/dactyl,moonshadow/dactyl,madand/pentadactyl-pm,nathyong/dactyl,moonshadow/dactyl,moonshadow/dactyl,invl/dactyl,airodactyl/dactyl,Kjwon15/dactyl