Switch mapping of purchase-events to use CompletePayment

[SimenHansen]

Suggestion to move the mapping of purchase events from PlaceAnOrder to CompletePayment

This comes after feedback from my local TikTok-rep on the Ads-side.
For correct optimization rules for the out-of-the-box bidding within TikTok a purchase-event should be tracked as CompletePayment.
The distinction being that PlaceAnOrder is meant for an order where you come back later to do the payment. More of a "soft"-conversion.

See also the definitions from TikTok Events

Place an Order | When a visitor places an order. TikTok recommends using this event when placing an order and making a payment are not the same.

Versus

Complete Payment |  When a visitor makes a payment. TikTok recommends using this event when placing an order and making a payment are the same.

[Bukashk0zzz]

@SimenHansen Thanks for the issue.
It is now fixed.