Docs: Move node install step before the brew one

What does this Merge Request do and why?

If you try to install yarn on the brew install step it will fail if you do not have node installed yet. This MR fixes that by installing node first.

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.