fixed: add astunparser to python<3.9 wheel

[victorbadenas]

In setup.py, sys.version_info.minor only returns the minor part of the version info. This check was never True and the wheel did not contain the extra dependency for python versions < 3.9.

Solves #603

After the fix, building the wheel locally with python 3.8:

$ make sdist
$ unzip dist/scalene-1.5.21.2-cp38-cp38-linux_x86_64.whl -d dist
$ cat dist/scalene-1.5.21.2.dist-info/METADATA | grep astunparse
Requires-Dist: astunparse (>=1.6.3)