Function: remove_links

--Usage--
> remove_links(input: card, linked_card: other card)
> remove_links(input: card, linked_relation: "link type")

Breaks the link between the input card and the linked_card. If a linked_relation is given, breaks the link between the input card and all cards with the linked_relation.

Returns an array containing all the cards that were unlinked.

--Parameters--
! Parameter	Type				Description
| @input@	[[type:card]] or [[type:string]]		One of the two cards we will unlink, or the uid of a card.
| @linked_card@	[[type:card]] or [[type:string]]		The other of the two cards we will unlink, or the uid of the other card.
| @linked_relation@	[[type:string]]		The type of link we will break.
| @set@		[[type:set]]		The set in which to look for the other card. This can be omitted since 'set' is a predefined variable.