sweep for py2k install directives, such as 'wheel=universal'

[zzzeek]

see sqlalchemy/alembic#893 for a similar issue in Alembic where 'wheel=universal' creates wheels targeted by py2 when people use pip. mako still has this. we should do a sweep to make sure the world of python 2 installers have zero chance of installing mako 1.2

[sqla-tester]

Michael Bourke has proposed a fix for this issue in the main branch:

Corrected universal wheel directive; building wheels now targets Python 3 only https://gerrit.sqlalchemy.org/c/sqlalchemy/mako/+/3437