sysutils/loki: Remove GH_TUPLE

GH_TUPLE is not required when using go:modules.
As a side-effect, this solves a hash issue in distfiles.

Approved by: portmgr (blanket)
Differential Revision: https://reviews.freebsd.org/D55695

(cherry picked from commit 02cf1b3851b540b042e67db4f8d42ab4c7f62bfe)