Simplify multi-cut condition

Now that the multi-cut condition is safer, we can avoid the cost of the sub-search.

STC:
https://tests.stockfishchess.org/tests/view/6165fd9283dd501a05b0b2fe
LLR: 2.93 (-2.94,2.94) <-2.50,0.50>
Total: 18648 W: 4745 L: 4600 D: 9303
Ptnml(0-2): 47, 2111, 4887, 2208, 71

LTC:
https://tests.stockfishchess.org/tests/view/616629ea83dd501a05b0b320
LLR: 2.96 (-2.94,2.94) <-2.50,0.50>
Total: 41704 W: 10407 L: 10302 D: 20995
Ptnml(0-2): 35, 4425, 11823, 4538, 31

closes https://github.com/official-stockfish/Stockfish/pull/3738

Bench: 5905086