Simplify Away Killer Condition in Cutnode LMR

Simplify Away Killer Condition in Cutnode LMR

Passed Non-regression STC:
LLR: 2.93 (-2.94,2.94) <-1.75,0.25>
Total: 42944 W: 11240 L: 11024 D: 20680
Ptnml(0-2): 159, 5056, 10825, 5274, 158
https://tests.stockfishchess.org/tests/view/669c13384ff211be9d4ec69f

Passed Non-regression LTC:
LLR: 2.96 (-2.94,2.94) <-1.75,0.25>
Total: 163548 W: 41366 L: 41289 D: 80893
Ptnml(0-2): 109, 18246, 45007, 18283, 129
https://tests.stockfishchess.org/tests/view/669cb1254ff211be9d4ec73a

closes https://github.com/official-stockfish/Stockfish/pull/5513

Bench: 1178570