Simplify stand pat adjustement
Remove && !PvNode condition for stand pat adjustement in quiescence search.
Passed non-regression STC:
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 108544 W: 28228 L: 28085 D: 52231
Ptnml(0-2): 389, 12902, 27554, 13031, 396
https://tests.stockfishchess.org/tests/view/66bb402e4ff211be9d4ee688
Passed non-regression LTC:
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 193014 W: 48796 L: 48751 D: 95467
Ptnml(0-2): 188, 21481, 53116, 21542, 180
https://tests.stockfishchess.org/tests/view/66bc78774ff211be9d4ee88f
closes https://github.com/official-stockfish/Stockfish/pull/5538
Bench 1787360