[CHANGE] Map challenges on easy and mediums clues

[Ainoyu Yunomi]

Why not make it like what was done with dipliation event and make it start at something like 1/5 chance to appear on map vote, after next map 1/4,..., until it always show up on the map vote.
This could slow down the amount of challenge maps appearing, providing removing them from easy/medium maps is not an option.