Falsify has_registered if an invoice containing an item from TICKET_PRODUCT_CATEGORY is refunded or voided

[jamezpolley]

• We've had cases where a person has had their ticket cancelled, but the system still has has_registered set to true
• This means that they show up in places they shouldn't - searches for attendees with has_registered show a bunch of people with 0 paid invoices.
• It also means they can't go through guided_registration again, because the fact that they have_registered makes things confused.

It would seem to make sense for any refund/void of an invoice containing an item from TICKET_PRODUCT_CATEGORY to remove the has_registered flag.