No Hope: Nerf spawn % of broken cyborg in basement_bionic

[themaster567]

Summary

Balance "No Hope: Reduce spawn chance of broken cyborgs in bionic basements"

Purpose of change

I feel like bionic_basement shouldn't have a 100% chance of spawning a broken cyborg. You know, because then you always know there's going to be a broken cyborg in it, meaning you can prepare for it in a way that I don't think was intended.

"It's a basement though, so how would yo-"

You hear "PLEASE GOD KILL ME AAAAAAAAAAAAAAAAAA" from 8 tiles away and below!

You know it's a bionic basement possibly before you even enter the house.

Describe the solution

Reduce the spawn chance of the broken cyborg in bionic basements from 100% to 25%.

Describe alternatives you've considered

Reducing it lower, keeping it higher, not changing it at all.

Testing

N/A: It's a single integer change.

Additional context

25% just feels right in my head, as I feel like there's a good chance that the cyborg resident holed up in a basement with no food would have wandered out into the world by the time the player arrives. However, I am completely down for discussing raising or lowering the number further if you think I'm off.

This PR was split from #77897 for simplicity so that one team could possibly decide differently from another without holding anything up.