Fix Python version comparison logic in post-gen hook

[minhsueh]

Issue:
The current string comparison sys.version.split(' ')[0] > '3.2' incorrectly evaluates to False for Python 3.11 (since '1' < '2'), causing the script to look for virtualenv instead of using the built-in venv module.

Proposed Change:
Use sys.version_info >= (3, 3) for a correct numerical comparison. This ensures modern Python environments use the native venv module as intended without requiring additional legacy dependencies.

Note:
While installing virtualenv manually can bypass the error, using sys.version_info is more robust to handle version checks in Python.

[alexcjohnson]

Good catch! We shouldn't need this conditional at all anymore, nothing in the Dash ecosystem these days supports such old Python versions.

[minhsueh]

Right, that makes sense. I’ve removed $ pip install virtualenv from the README and now use venv = '{} -m venv venv'.format(sys.executable) as the default.

[alexcjohnson]

Thanks! Looking around this repo there are a bunch of other out-of-date elements, like we're still generating a setup.py file rather than pyproject.toml. If you're motivated to continue improving this we'd welcome another PR, but I'll also see if someone at Plotly can give it a look.