Remove condition for pawn threats

Remove condition for pawn threats

It appears as though removing squares that are already attacked
by our pawns can be removed.

STC
LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 51242 W: 11503 L: 11440 D: 28299
http://tests.stockfishchess.org/tests/view/5b58b5a40ebc5902bdb88f52

LTC
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 35246 W: 6063 L: 5966 D: 23217
http://tests.stockfishchess.org/tests/view/5b58f8e20ebc5902bdb8959b

How to continue after this patch: there is now a slight semantic
overlap between the ThreatByPawnPush and the ThreatBySafePawn bonuses,
so hand-tuning either of these, or both at the same time, is natural.

Closes https://github.com/official-stockfish/Stockfish/pull/1702

Bench 4734881