devel/py-rebulk: update to 3.0.1

• Add python 3.8/3.9 support, drop python 2.7/3.4 support

Changelogs: https://github.com/Toilal/rebulk/releases

PR: 252100
Submitted by: Nuno Teixeira <ed.arrakis@gmail.com>
Approved by: arrowd, tcberner (mentors, implicit)