Drop Python 3.3 and Python 3.4

Because github actions is dropping support for Ubuntu-18.04 and Ubuntu-18.04 is the only Linux platform that supports running Python 3.3 and Python 3.4 from actions, we'll need to drop support for it given it would be much harder to test it.

Unless somebody steps in to provide CI config to test on p3.3 and py3.4, those python versions will be dropped in the next release.