[continuous-integration] fix and clean up macOS.yml

[superwhd]

There are macOS workflow failures for new PRs like this:

Error: No such keg: /opt/homebrew/Cellar/pkg-config

I checked macos-14-Readme.md and noticed that some dependencies (like pkg-config) of the macOS workflow are already satisfied by the image so we don't have to reinstall them again.

Also, this PR removes dbus in the macOS workflow because D-BUS is not enabled when building OTBR.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 45.92%. Comparing base (2b41187) to head (bd62412).
Report is 882 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2619      +/-   ##
==========================================
- Coverage   55.77%   45.92%   -9.86%     
==========================================
  Files          87      106      +19     
  Lines        6890    12624    +5734     
  Branches        0      915     +915     
==========================================
+ Hits         3843     5797    +1954     
- Misses       3047     6511    +3464     
- Partials        0      316     +316     

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[Irving-cl]

LGTM 👍