Update macro related documentation to remove reference to registers 0-9.
Update macro related documentation to remove reference to registers 0-9.

These are no longer available for recording.  The restriction seems rather
arbitrary so they may return.

Fixes issue #1103.

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