NCC audit: Define \mathbb{G} in \crossref{concretegrouphashpallasandvesta}.
NCC audit: Define \mathbb{G} in \crossref{concretegrouphashpallasandvesta}.

Signed-off-by: Daira Hopwood <cd7d43d5556a38ce626d53826fddc46adc597539@jacaranda.org>

zcash/zips,zcash/zips,zcash/zips,zcash/zips