Simplify captures PCM
Passed Non-regression STC:
LLR: 2.92 (-2.94,2.94) <-1.75,0.25>
Total: 229856 W: 59258 L: 59252 D: 111346
Ptnml(0-2): 746, 27330, 58714, 27448, 690
https://tests.stockfishchess.org/tests/view/67d3fdac517865b4a2dfcef4
Passed Non-regression LTC:
LLR: 2.95 (-2.94,2.94) <-1.75,0.25>
Total: 107652 W: 27470 L: 27338 D: 52844
Ptnml(0-2): 56, 11646, 30280, 11798, 46
https://tests.stockfishchess.org/tests/view/67d5f972517865b4a2dfd2ec
closes https://github.com/official-stockfish/Stockfish/pull/5931
Bench: 1842520