Add proper lake to tutorial map

Lake was not showing properly in a24 anymore.
Reported by gameboy on forum: https://wildfiregames.com/forum/topic/34502-the-disappearing-lake/
Cause is, that water level had the same value as terrain level and since a24 uses more precise water level computation, high quality water effects did not show the lake. ( found by @vladislavbelov )

Rise water level in the lake, remove animals, trees, minerals from lake area add some fish.

Differential Revision: D3240