Fix vehicle_split_section test by only destroying the vehicle and not the terrain

[mqrause]

Summary

None

Purpose of change

More stable CI.

Describe the solution

The test was producing a lot of false positives due to destroying terrain under the vehicle, which sometimes could cause collapses that apparently destroyed more vehicle parts. Destroying terrain or anything other than vehicles is irrelevant for the test, so only destroy vehicles.

Describe alternatives you've considered

Testing

Run tests with --rng-seed 1735408622 vehicle_split_section. Note that without this change there was also the curious case that it only failed every second run. Somehow there were additional rng events happening in the runs that passed which ultimately resulted in different rng rolls for the terrain destruction/collapse, but I didn't manage to get to the source of that.

Additional context

[osuphobia]

You forgot to replace the one in Line 76 so it's still failing👀