Remove time reduction for recaptures

Passed simplification STC
LLR: 2.96 (-2.94,2.94) <-1.75,0.25>
Total: 54016 W: 14098 L: 13902 D: 26016
Ptnml(0-2): 165, 5797, 14919, 5931, 196
https://tests.stockfishchess.org/tests/view/6758a90486d5ee47d954201e

Passed simplification LTC
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 296940 W: 75631 L: 75689 D: 145620
Ptnml(0-2): 145, 28928, 90384, 28866, 147
https://tests.stockfishchess.org/tests/view/6758df7a86d5ee47d9542091

closes https://github.com/official-stockfish/Stockfish/pull/5719

Bench: 1148169

src/engine.h

@@ -39,8 +39,6 @@
 
 namespace Stockfish {
 
-enum Square : int;
-
 class Engine {
    public:
     using InfoShort = Search::InfoShort;
@@ -116,7 +114,6 @@ class Engine {
 
     Position     pos;
     StateListPtr states;
-    Square       capSq;
 
     OptionsMap                               options;
     ThreadPool                               threads;