Fix "Via Python" Instructions

[wesleyboar]

Problem

I think the "A. Via Python" instructions are not accurate. When I tried to follow them fresh and blind, I get ModuleNotFoundError: No module named 'poetry.core.toml'. I worry previous success occurred only because I had a virtual env active without knowing it.

Solution

Change "A. Via Python" instructions to first suggest reader set up a "venv" (however they want, because there are so many ways), then run the commands, but without poetry shell (which is a Poetry env shortcut I don't really understand).

Reference

A report from a new user that successfully set up User Guide via Python did this:

I first ran brew install [email protected] [then] created a virtualenv using that version of python with python3.12 -m venv designsafe_venv, activated the virtualenv, and then followed what was in the instructions on the Github repo:

pip install poetry
./bin/tacc-setup.sh
poetry install
poetry shell
cd user-guide
mkdocs serve