Simplify threat term in movepick
Passed simplification STC
LLR: 2.97 (-2.94,2.94) <-1.75,0.25>
Total: 71296 W: 18605 L: 18419 D: 34272
Ptnml(0-2): 250, 8374, 18183, 8622, 219
https://tests.stockfishchess.org/tests/view/690454c7ea4b268f1fac1bbe
Passed simplification LTC
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 240552 W: 61870 L: 61874 D: 116808
Ptnml(0-2): 113, 26300, 67460, 26284, 119
https://tests.stockfishchess.org/tests/view/69063956ea4b268f1fac1f66
closes https://github.com/official-stockfish/Stockfish/pull/6401
bench 2697501