astro/py-spktype01 et al.: fix the dependency on PYNUMPY

Some ports, like astro/py-spktype01, uses the undefined variable ${NUMPY}
in their _DEPENDS fields and this must be replaced by the correct
${PYNUMPY}.

PR:		254740
Reported by:	Bojan Petrovic
Approved by:	QA blanket for the ports that I do not maintain