Put zsh completions in correct place in homebrew bottle, fixes #2317

[rfay]

The Problem/Issue/Bug:

#2317: Zsh and fish completions were not being placed properly in the homebrew bottle.

How this PR Solves The Problem:

Put them in the correct place.

Manual Testing Instructions:

• brew uninstall ddev
• Verify that the zsh completions are gone
• brew install ddev
• Verify that zsh and fish completions have been properly added to /usr/local/share/zsh/site-functions and that they work

It should say

zsh functions have been installed to:
  /usr/local/share/zsh/site-functions

Automated Testing Overview:

Related Issue Link(s):

OP #2317

Release/Deployment notes:

This needs to be tested after next alpha release