Clean up old graphbook files and onboarding docs

Created by: christinaforney

Moved account setup to general onboarding and removed the additional docs for onboarding that are no longer necessary. (Note this is based on my product onboarding PR update).

@mercadon - I am assuming that you aren't using the checklists on the us/non-us/sf based teammates pages anymore and that they can be removed. If not, we can quickly consolidate into a single clear document.