Rework RemoveCounterCost about mage

[github-actions]

Mari, the Killing Quill - (Gatherer) (Scryfall) (EDHREC)

{1}{B}{B}
Legendary Creature — Vampire Assassin
3/2
Whenever a creature an opponent controls dies, exile it with a hit counter on it.
Assassins, Mercenaries, and Rogues you control have deathtouch and "Whenever this creature deals combat damage to a player, you may remove a hit counter from a card that player owns in exile. If you do, draw a card and create two Treasure tokens."

Falco Spara, Pactweaver - (Gatherer) (Scryfall) (EDHREC)

{1}{G}{W}{U}
Legendary Creature — Bird Demon
3/3
Flying, trample
Falco Spara, Pactweaver enters the battlefield with a shield counter on it.
You may look at the top card of your library any time.
You may cast spells from the top of your library by removing a counter from a creature you control in addition to paying their other costs.

[JayDi85]

Yes, it must be improved. Each related cost usage must be carefully reviewed -- if you put filter to current target (CounterType already has predicates) then it will fail due unsupported canPay method (see zero counters use case on X = 0):

P.S. Not related to issue -- looks like MariTheKillingQuill and OblivionSower uses wrongly face-up predicate (I don't see any requirements for it):