Update gcloud installation instructions in the Kubernetes How-To doc

What does this Merge Request do and why?

Update the gcloud installation instructions in the Kubernetes How-To doc.

Mac machines using Apple silicon have the Homebrew directory in /opt/homebrew.

This update ensures that the command added on the developer's profile points to files in the correct directory

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 Issue to follow-up.
• Documentation added/updated, if needed.
• gdk doctor test added, if needed.
• Add the ~highlight label if this MR should be included in the CHANGELOG.md.