Remove agricultural location from craters to prevent intermittent failures in oermap generation

[kevingranade]

Summary

None

Purpose of change

I've been seeing intermittent failures in the overmap_terrain_coverage test due to placement of these Crater specials.

Describe the solution

I noticed a correlation with rural roads being reported and tried just removing the agricultural location from the special definition.

Describe alternatives you've considered

Removing Craters is an option, but I'd rather not throw them away over a flaw in the system.
There's definitely some underlying issue here that I haven't spotted, but I don't know what it is.

Testing

I ran the test repeatedly (a thousand times) overnight with the following invocation:
printf 'overmap_terrain_coverage\n%.0s' {0..1000} | parallel --bar -j 5 "tests/cata_test "{}" | tee big_test_results/test_{#}"
This invokes up to 5 instances of the test in parallel and writes their results out to files in the given subdirectory.
In previous testing I saw this failure more like one time out of a hundred, so it's very unlikely I saw this many passes without addressing the issue.

[Procyonae]

Wouldn't adding a new overmap_location that's just agricultural but without rural_road and adding a comment referencing this be better?

[kevingranade]

Do you fully understand what's happening here? I'm just treating symptoms.

#73429 adjusts the crater definition to fall back to placing small craters if it can't place anything next to the root, which seems better than my change in principle, though I'm a bit concerned with how much effort these take to troubleshoot.

[Procyonae]

Nah I were just suggesting a less aggressive fix if you thought the issue was definitely connected to rural roads, #73429 makes sense as a fix though, it's unfortunate making an errorless mutable is as much an art as a science