Remove tapping of homebrew/cask

What does this merge request do and why?

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

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Ensuring platform software installed
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INFO: Setting up 'darwin' platform..
Warning: Tapping homebrew/cask is no longer typically necessary.
Add --force if you are sure you need it done.
==> Tapping homebrew/cask

Impacted categories

The following categories relate to this merge request:

• gdk-reliability - e.g. When a GDK action fails to complete.
• gdk-usability - e.g. Improvements or suggestions around how the GDK functions.
• gdk-performance - e.g. When a GDK action is slow or times out.

Merge request checklist

• This change is backward compatible. If not, please include steps to communicate to our users.
• Tests added for new functionality. If not, please raise an issue to follow-up.
• Documentation added/updated, if needed.
• Announcement added, if change is notable.
• gdk doctor test added, if needed.
• Add the ~highlight label if this MR should be included in the CHANGELOG.md.