Make ProbCut search shallower in cutNode
Passed STC:
https://tests.stockfishchess.org/tests/view/6832d2436ec7634154f9b4fc
LLR: 2.93 (-2.94,2.94) <0.00,2.00>
Total: 455072 W: 118162 L: 117237 D: 219673
Ptnml(0-2): 1233, 53409, 117362, 54264, 1268
Passed LTC:
https://tests.stockfishchess.org/tests/view/6833323e6ec7634154f9ba17
LLR: 2.95 (-2.94,2.94) <0.50,2.50>
Total: 128436 W: 32916 L: 32415 D: 63105
Ptnml(0-2): 50, 13737, 36137, 14250, 44
closes https://github.com/official-stockfish/Stockfish/pull/6093
Bench: 2232447