[Art][Gameplay] A slightly larger chicken model to improve gameplay

This creates a slightly larger chicken model, which helps with visual identification at the start of the match. I have seen multiple let's plays where finding the initial chickens took too long (in my opinion), because I believe they are too small for the game world.

Patch by: @wowgetoffyourcellphone
Original model by: @Langbart
Accepted by: @chrstgtr, @real_tabasco_sauce

Differential revision: https://code.wildfiregames.com/D5177