Simplify eval >= beta condition from NMP
It seems that now only checking if static eval is above beta by some margin is all that's necessary.
Passed Non-Regression STC
LLR: 2.93 (-2.94,2.94) <-1.75,0.25>
Total: 227264 W: 58430 L: 58421 D: 110413
Ptnml(0-2): 532, 26559, 59454, 26542, 545
https://tests.stockfishchess.org/tests/view/68763a77432ca24f6388c766
Passed Non-Regression LTC
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 72048 W: 18622 L: 18455 D: 34971
Ptnml(0-2): 26, 7775, 20272, 7908, 43
https://tests.stockfishchess.org/tests/view/687c9f2b6e17e7fa3939b0c5
closes https://github.com/official-stockfish/Stockfish/pull/6175
Bench: 2759840