macos CI: use brew trust (backport #826)

[mergify]

🦟 Bug fix

Similar to gazebo-tooling/release-tools#1508

Summary

Homebrew's package descriptions (formulae) are implemented as executable ruby code, which can lead to security issues when using 3rd-party taps, so they have recently added a brew trust command to help mitigate security issues, documented here. It is now required to use brew trust osrf/simulation after brew tap osrf/simulation in order to run additional commands like brew install gz-jetty. I have updated the macos workflow script to fix it, as it is currently broken.

Backport Policy

• This is safe to backport to the following versions:
  • Jetty
  • Ionic
  • Harmonic
  • Fortress
• This should not be backported
• I am not sure
• Other (fill in yourself)

Checklist

• Signed all commits for DCO
• Added a screen capture or video to the PR description that demonstrates the fix (as needed)
• Added tests
• Updated documentation (as needed)
• Updated migration guide (as needed)
• Consider updating Python bindings (if the library has them)
• codecheck passed (See contributing)
• All tests passed (See test coverage)
• Updated Bazel files (if adding new files). Created an issue otherwise.
• While waiting for a review on your PR, please help review another open pull request to support the maintainers
• Was GenAI used to generate this PR? If so, make sure to add "Generated-by" to your commits. (See this policy for more info.)

Note to maintainers: Remember to use Squash-Merge and edit the commit message to match the pull request summary while retaining Signed-off-by and Generated-by messages.

Backports: If this is a backport, please use Rebase and Merge instead.

---

This is an automatic backport of pull request #826 done by Mergify.