remove brew update command from ci

[collinc97]

Issue

Run brew update
error: Could not read 050b5490e7bb098f70f3de925431a24622f2d64c
fatal: revision walk setup failed
error: https://github.com/Homebrew/homebrew-cask did not send all necessary objects

GitHub actions CI failing due to broken brew update command on macos m1 platforms

Breaking in all current PRs.
Example https://github.com/AleoHQ/leo/actions/runs/5463254559/jobs/9943707212?pr=2443

Fix

Removing brew update from CI as referenced in https://github.com/orgs/Homebrew/discussions/4612#discussioncomment-6356325

[codecov]

Codecov Report

Merging #2445 (4ad753d) into testnet3 (c0b2778) will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##           testnet3    #2445   +/-   ##
=========================================
  Coverage     79.23%   79.23%           
=========================================
  Files           154      154           
  Lines          4868     4868           
  Branches       4867     4867           
=========================================
  Hits           3857     3857           
  Misses         1011     1011           

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[d0cd]

LGTM!