Sets all pricing plans as not primary.
The clearPrimary() function returns a Promise that resolves when no pricing plan is
marked as a primary plan.
After clearing the primary plan, when viewing pricing plans on the site, no plan is highlighted with a customizable ribbon.
Only users with "Manage Pricing Plans" permissions can clear the primary plan.
This method doesn’t return any custom errors, but may return standard errors. Learn more about standard Wix errors.