Tweak knight mobility

Tweak knight mobility

New tuned values for knight mobility in endgames.

STC:
LLR: 2.94 (-2.94,2.94) {-0.50,1.50}
Total: 112576 W: 21999 L: 21644 D: 68933
Ptnml(0-2): 2009, 13084, 25735, 13463, 1997
https://tests.stockfishchess.org/tests/view/5ec58379377121ac09e10272

LTC:
LLR: 2.95 (-2.94,2.94) {0.25,1.75}
Total: 125192 W: 16200 L: 15671 D: 93321
Ptnml(0-2): 891, 11584, 37182, 11983, 956
https://tests.stockfishchess.org/tests/view/5ec5c0b8377121ac09e1028b

Closes https://github.com/official-stockfish/Stockfish/pull/2693

Bench: 4778956