Simplify Return Value Adjustment Condition
Passed Non-regression STC:
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 82112 W: 21281 L: 21110 D: 39721
Ptnml(0-2): 258, 9630, 21112, 9795, 261
https://tests.stockfishchess.org/tests/view/67c42528b7226b5d8a2dd3a0
Passed Non-regression LTC:
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 182652 W: 46295 L: 46240 D: 90117
Ptnml(0-2): 103, 20025, 51003, 20104, 91
https://tests.stockfishchess.org/tests/view/67c4d56b685e87e15e7c43d8
closes https://github.com/official-stockfish/Stockfish/pull/5925
Bench: 1711791