Update setup.py PyPI classifiers

[fedarko]

Not a big deal, but the python versions listed here were out of date. I'm basing the versions listed here on the python versions we currently test against in the standalone CI:

https://github.com/biocore/empress/blob/95848b854d3703c539972ed407d7722b61fad2c2/.github/workflows/standalone.yml#L23

I'm not sure if we ever decided officially to not support Python 3.5 or if we just quietly abandoned testing against it. In any case, I don't see a reason to maintain support for it (for reference the latest version of QIIME 2 is already on Python 3.8.8).

Aside from updating the python version classifiers I also added a few relevant classifiers from Qurro's setup.py (bioinformatics, visualization, etc), and removed the application framework classifier. (I don't think Empress qualifies as an "application framework," but I just spent a solid minute staring at the first sentence of this Wikipedia article and I'm still not sure so IDK.)

[emperor-helper]

The following artifacts were built for this PR: empire-biplot.qzv, empire.qzv, empress-tree.qzv, just-fm.qzv, plain.qzv

[ElDeveloper]

Thanks @fedarko.

[fedarko]

Thanks @ElDeveloper!