fix - changes in the install.sh for misplaced single quote.

[Rushour0]

A single quote was misplaced in the section of Run these two commands in your terminal to add Homebrew
Fixing this will make the post install process run smoothly without any hiccup.

[Bo98]

Original looks correct:

            v_______________________________________________v
(echo; echo 'eval "\$(${HOMEBREW_PREFIX}/bin/brew shellenv)"')
^____________________________________________________________^
                     ^____________________________________^

[Rushour0]

The original was probably misse read on my terminal