Remove check extension

Remove check extension

Passed simplification STC:
https://tests.stockfishchess.org/tests/view/65c38d2ac865510db02836cf
LLR: 2.93 (-2.94,2.94) <-1.75,0.25>
Total: 52288 W: 13578 L: 13371 D: 25339
Ptnml(0-2): 197, 6171, 13265, 6250, 261

Passed simplification LTC:
https://tests.stockfishchess.org/tests/view/65c4470ec865510db0284473
LLR: 2.95 (-2.94,2.94) <-1.75,0.25>
Total: 44958 W: 11255 L: 11055 D: 22648
Ptnml(0-2): 37, 4962, 12274, 5176, 30

closes https://github.com/official-stockfish/Stockfish/pull/5041

Bench: 1116591