tests: revert testing against prerelease deps on Python 3.9#426

Merged

gcf-merge-on-green[bot] merged 2 commits intomasterfrom revert-415-414-test-against-prerelease-deps-under-3.9

Aug 18, 2021

-2

Commits on Aug 17, 2021

Revert "tests: allow prerelease deps on Python 3.9 (#415 )"
tseaver
authored

Commits on Aug 18, 2021

Merge branch 'master' into revert-415-414-test-against-prerelease-deps-under-3.9
tseaver
authored