Update default net to nn-308d71810dff.nnue

Update default net to nn-308d71810dff.nnue

equivalent to 20200903-1739

Net trained from scratch, so it has quite different features extracted compared to the previous net (82215d0fd0df).

STC:
LLR: 2.98 (-2.94,2.94) {-0.25,1.25}
Total: 108328 W: 14048 L: 13719 D: 80561
Ptnml(0-2): 842, 10039, 32062, 10390, 831
https://tests.stockfishchess.org/tests/view/5f50e053ba100690c5cc5f00

LTC:
LLR: 2.96 (-2.94,2.94) {0.25,1.25}
Total: 13872 W: 1059 L: 890 D: 11923
Ptnml(0-2): 30, 724, 5270, 871, 41
https://tests.stockfishchess.org/tests/view/5f51821fba100690c5cc5f36

closes https://github.com/official-stockfish/Stockfish/pull/3104

Bench: 3832716