Simplifying mac installation instructions with HOMEBREW_PREFIX

[milespossing]

Uses the $HOMEBREW_PREFIX environment variable rather than the absolute paths. This abstracts away from using the explicit path and works for most custom homebrew installations on MacOS

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[milespossing]

Hey all, this is just a very very minor documentation quirk I noticed. It would be much easier for all users to simply use the variable which homebrew sets

[milespossing]

I had a friend check their HOMEBREW_PREFIX env var and it was not on their machine. Closing until I can verify on intel macs