Use less reduction for escaping moves

This patch reuses the threatenedPieces variable (which is calculated in movepicker)
to reduce less in the search tree the moves which escape a capture.

passed STC:
LLR: 2.94 (-2.94,2.94) <0.00,2.00>
Total: 314352 W: 84042 L: 83328 D: 146982
Ptnml(0-2): 1105, 35084, 84207, 35552, 1228
https://tests.stockfishchess.org/tests/view/63355f37a004bed9a2e4a17f

passed LTC:
LLR: 2.95 (-2.94,2.94) <0.50,2.50>
Total: 90752 W: 24556 L: 24147 D: 42049
Ptnml(0-2): 59, 8855, 27123, 9296, 43
https://tests.stockfishchess.org/tests/view/63383a7735f43d649ff5fa8b

closes https://github.com/official-stockfish/Stockfish/pull/4181

bench: 4114228

src/evaluate.cpp

@@ -1054,7 +1054,7 @@ Value Eval::evaluate(const Position& pos, int* complexity) {
   Color stm = pos.side_to_move();
   Value psq = pos.psq_eg_stm();
 
-  // We use the much less accurate but faster Classical eval when the NNUE 
+  // We use the much less accurate but faster Classical eval when the NNUE
   // option is set to false. Otherwise we use the NNUE eval unless the
   // PSQ advantage is decisive and several pieces remain (~3 Elo)
   bool useClassical = !useNNUE || (pos.count<ALL_PIECES>() > 7 && abs(psq) > 1760);