doc: update Homebrew installation docs.
doc: update Homebrew installation docs.

Fucking undocumented moving target. Why is it not possible to install
from a file anymore?! Why make things unnecessarily complicated?!

mosra/magnum-examples,Squareys/magnum-examples,mosra/magnum-examples,mosra/magnum-examples,Squareys/magnum-examples,mosra/magnum-examples,mosra/magnum-examples,Squareys/magnum-examples,Squareys/magnum-examples,mosra/magnum-examples,mosra/magnum-examples