remove homebrew release step

[kevinAlbs]

Summary

Remove Homebrew release step.

Background & Motivation

Homebrew steps were also removed from C driver in mongodb/mongo-c-driver#1687.

Trying to manually update results in this message:

% brew bump-formula-pr mongo-cxx-driver --url https://github.com/mongodb/mongo-cxx-driver/releases/download/r3.10.2/mongo-cxx-driver-r3.10.2.tar.gz
Error: Whoops, the mongo-cxx-driver formula has its version update
pull requests automatically opened by BrewTestBot every ~3 hours!
We'd still love your contributions, though, so try another one
that's not in the autobump list:
  https://github.com/Homebrew/homebrew-core/blob/master/.github/autobump.txt