Simplify away optimism average score offset params
Passed non-regression STC:
https://tests.stockfishchess.org/tests/view/654abf6b136acbc57352ac4b
LLR: 2.97 (-2.94,2.94) <-1.75,0.25>
Total: 49664 W: 12687 L: 12477 D: 24500
Ptnml(0-2): 138, 5840, 12703, 5976, 175
Passed non-regression LTC:
https://tests.stockfishchess.org/tests/view/654b638e136acbc57352b961
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 347166 W: 85561 L: 85676 D: 175929
Ptnml(0-2): 206, 39569, 94150, 39450, 208
closes https://github.com/official-stockfish/Stockfish/pull/4871
bench 1257641