docs: consolidate dependency management into top-level config

[ITProKyle]

Summary

Remove the need to manage two different virtual environments (app & docs). The dependencies to build docs are now managed from the top-level pyproject.toml file.

These dependencies are added as extras due to a limitation of ReadTheDocs (does not support poetry) and poetry (can't install dev dependencies using pip).

What Changed

Added

• added docs extra dependencies to top-level pyproject.toml

Changed

• poetry will now remove untracked dependencies when running make setup
• poetry will install the docs extra dependencies when running make setup

Removed

• removed dedicated venv/dependency management used for docs