Cataclysm-dda: New map extras from the long grass PR Erk made have unreasonably high spawn rates.

[Amoebka]

Describe the bug

https://github.com/CleverRaven/Cataclysm-DDA/pull/35990 introduced new map extras for fields. Spawn rates feel extremely off, desolate sheds and ponds are absolutely everywhere.
Did you forget to turn down the spawn rates after testing?

Steps To Reproduce

Steps to reproduce the behavior:

1. Make a world.
2. Run around a field.
3. Barns and ponds are like 10% of all field tiles.

Expected behavior

Barns and ponds should be rare. Tree patches should be less common.

Versions and configuration

• OS: win10
• Game Version: 0.D-10453-g572b78f
• Graphics version: tiles
• Mods loaded: none

Additional context

Fields mapgen has gone berserk, with this chant I summon @I-am-Erk.

[I-am-Erk]

I'm already working on it, no need to call me out in the issue title

[kevingranade]

Erk may or may not be joking, but calling people out in issues is bad form so please don't do it.

[I-am-Erk]

I'm only a little joking, I'm not really offended but I could easily see someone else being.