Docs: Installation for MacOS + conda says to use Python 3.8, but installation fails unless a newer version of python is used

[jcowles]

Describe the bug

Follow the anaconda instructions from the installation page, which says to use this command:

conda create -n manim python=3.8

This will fail, but this will succeed:

conda create -n manim

The installation fails when running:
pip install -e .

after the fix proposed above, this command must be:
pip3 install -e .