manual/groveller: fix ctype's documentation
manual/groveller: fix ctype's documentation

Reported by Stelian Ionescu.

stassats/cffi,stassats/cffi,akovalenko/cffi,akovalenko/cffi,cffi/cffi,marsijanin/cffi,dkochmanski/cffi,marsijanin/cffi,dochang/cffi,dkochmanski/cffi,cffi/cffi,dochang/cffi,dochang/cffi,attila-lendvai/cffi,mcna/cffi,dkochmanski/cffi,wesen/cffi,kingcheez/cffi-cheez,akovalenko/cffi,3b/cffi,cffi/cffi,kingcheez/cffi-cheez,wesen/cffi,mcna/cffi,stassats/cffi,marsijanin/cffi,kingcheez/cffi-cheez,wesen/cffi,attila-lendvai/cffi,3b/cffi,3b/cffi