graphics/openpgl: remove TBB option

Disabling the TBB option didn't work and does not appear to be
immediately fixable. Remove the option as a workaround until
a solution obtains.

PR: 268779
Reported by: Matthieu Volat <mazhe@alkumuna.eu>
Approved by: flo (mentor)
Differential Revision: https://reviews.freebsd.org/D38777