lang/tauthon: Update to 2.8.3

ChangeLog: https://github.com/naftaliharris/tauthon/blob/master/Misc/NEWS.d/2.8.3.rst

PR: 256387
Reported by: olivier.freebsd@free.fr (maintainer)
Security: CVE-2020-8492
MFH: 2021Q2

(cherry picked from commit 7d98dad380fae35c1a1f64e1b86c3488aef24d0f)