Remove defunct Makefile targets

[KueZie]

Root Makefile contains defuct targets including but not limited to:

install:
  python3 -m venv .
  . bin/activate && pip install -r requirements-dev.txt

This functionality seems to have been ported to tox.ini and was never removed.

[slott56]

After looking at the Makefile, my suggestion on deleting was a bad idea.

I don't think it should be deleted. I think it needs to be rewritten to use poetry properly instead of trivially deleted.

[kapilt]

addressed in #87