astro/astroterm: Update 1.1.0 => 1.2.0

While here, switch to upstream-preferred, maintained devel/argtable3.

Changelog:
https://github.com/da-luce/astroterm/releases/tag/v1.2.0

Reviewed by: osa (mentor), vvd (co-mentor)
Approved by: vvd (co-mentor)
Differential Revision: https://reviews.freebsd.org/D56258