Mk/bsd.port.mk: Remove duplicate variable in JSON output

Remove duplicate pkg_depends when generating a JSON description of the three

Approved by:		delphij@
Fixes:			3d9f300
Differential Revision: https://reviews.freebsd.org/D42373

Mk/bsd.port.mk

@@ -4442,7 +4442,6 @@ describe-json:
 	${ECHO_CMD} \"pkgnamesuffix\":\"${PKGNAMESUFFIX}\", ;\
 	${ECHO_CMD} \"pkgorigin\":\"${PKGORIGIN}\", ;\
 	${ECHO_CMD} \"comment\":\"${COMMENT:Q:S/"/\\\"/g:S/\\\\*/*/g:S/\\\'/'/g}\", ;\
-	${ECHO_CMD} \"pkg_depends\":\"${PKG_DEPENDS}\", ;\
 	${ECHO_CMD} \"portepoch\":\"${PORTEPOCH}\", ;\
 	${ECHO_CMD} \"portname\":\"${PORTNAME}\", ;\
 	${ECHO_CMD} \"portrevision\":\"${PORTREVISION}\", ;\