Rat mutation tree results in carnivore due to requirements

[dissociativity]

Describe the bug
Intestinal fortitude requires Saprovore, this results in the rat mutation tree getting carnivore.
Rats are omnivores.

To Reproduce
Steps to reproduce the behavior:

1. Inject Rat Serum
2. repeat
3. get carnivore

Expected behavior
Not getting mutations that aren't in the rat mutation tree.

Screenshots
Unnecessary

Versions and configuration(please complete the following information):

• OS: Windows 8.1
• Game Version Build from 6/01/2019 (DD/MM/YYYY)
• Graphics version: Tiles
• Mods loaded: none, happens regardless

Additional context
not required as this is a simpler issue

[kevingranade]

I'm not against changing it, but this isn't a bug per se. It's intended that you get all kinds of out-of-tree mutations as you mutate.

[PsyXypher]

Well, perhaps that doesn't need to be "fixed", but perhaps a change can be made so Carnivore gets cancelled out by another mutation later on (Rapid Metabolism, maybe?). The other "solution" is to make it so you could randomly get Substance Tolerance (I'm not sure if this is already possible or not) which also works as a requirement for Intestinal Fortitude, and would be a suitable replacement.

[dissociativity]

The issue with this is strictly injecting rat serum causes it.

[sneeze-attack]

We could remove the carnivore requirement from saprovore. The other idea is to cancel out carnivore when reaching rat post-thresh.

I'm leaning towards removing the carnivore requirement, but both should be valid solutions. @dissociativity do you think one idea is better than other?

[kevingranade]

Fixed by #28176