`Deck` objects don't properly filter elemental hero cards.

[HarrisonTotty]

Describe the bug
The cards an elemental hero can play are designated in the body of the card, as opposed to its types. Therefore, any calls to filter_related() will be inaccurate.

To Reproduce
Create a Briar deck.

all_cards = [] # contains all cards ...
briar = Card.from_full_name('Briar')
deck = Deck(name='test', hero=briar)
deck.filter_related(all_cards)

Expected behavior
You should see Earth and Lightning cards in the list.