databases/grass7: unbreak after gdal 3.3 update

GDAL 3.3.0 introduces the use of standard C bool type.
Redefining bool locally, as in vector/v.hull/chull.c causes failure.

Obtained from: https://github.com/OSGeo/grass/pull/1567

(cherry picked from commit 562f7a0402ea5aa193f618ed6da3775a631f249a)