[ty] Re-enable multithreaded pydantic benchmark (#19176)
## Summary
I played with those numbers a bit locally and `sample_size=3,
sample_count=8` seemed like a rather stable setup. This means a single
sample consistents of 3 iterations of checking pydantic multithreaded.
And this is repeated 8 times for statistics. A single check took ~300 ms
previously on the runners, so this should only take 7 s.
