Simplify KingProtector penalty.

Simplify KingProtector penalty.

Recent tuning results implied this penalty is more important for knights
and bishops, and almost negligible for rooks and queen.

Passed as simplification both
STC
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 20873 W: 4592 L: 4469 D: 11812
http://tests.stockfishchess.org/tests/view/5b2fb4d00ebc5902b2e57e84

and LTC
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 46069 W: 7949 L: 7870 D: 30250
http://tests.stockfishchess.org/tests/view/5b2fcc4b0ebc5902b2e580c5

Closes https://github.com/official-stockfish/Stockfish/pull/1660

Bench: 5487679