⚡ Stop checking for two/threefold repetition and 50 moves draws in QS…

…earch (#673)

As of now, QSearch only searches captures, pawn promotions and castling moves.
Only the latter could produce a 50 moves repetition, and none of them could produce a two/threefold one.

So it's pointless to check for repetition inside of QSearch.

src/Lynx/Search/NegaMax.cs

@@ -546,32 +546,10 @@ public int QuiescenceSearch(int ply, int alpha, int beta)
 
             PrintPreMove(position, ply, move, isQuiescence: true);
 
-            // Before making a move
-            var oldValue = Game.HalfMovesWithoutCaptureOrPawnMove;
-            Game.HalfMovesWithoutCaptureOrPawnMove = Utils.Update50movesRule(move, Game.HalfMovesWithoutCaptureOrPawnMove);
-            var isThreeFoldRepetition = !Game.PositionHashHistory.Add(position.UniqueIdentifier);
-
-            int evaluation;
-            if (isThreeFoldRepetition || Game.Is50MovesRepetition())
-            {
-                evaluation = 0;
-
-                // We don't need to evaluate further down to know it's a draw.
-                // Since we won't be evaluating further down, we need to clear the PV table because those moves there
-                // don't belong to this line and if this move were to beat alpha, they'd incorrectly copied to pv line.
-                Array.Clear(_pVTable, nextPvIndex, _pVTable.Length - nextPvIndex);
-            }
-            else
-            {
-                evaluation = -QuiescenceSearch(ply + 1, -beta, -alpha);
-            }
+            // No need to check for threefold or 50 moves repetitions, since we're only searching captures, promotions, and castles
+            // Theoretically there could be a castling move that caused the 50 moves repetitions, but it's highly unlikely
 
-            // After making a move
-            Game.HalfMovesWithoutCaptureOrPawnMove = oldValue;
-            if (!isThreeFoldRepetition)
-            {
-                Game.PositionHashHistory.Remove(position.UniqueIdentifier);
-            }
+            int evaluation = -QuiescenceSearch(ply + 1, -beta, -alpha);
             position.UnmakeMove(move, gameState);
 
             PrintMove(ply, move, evaluation);