Assorted small cleanups

closes https://github.com/official-stockfish/Stockfish/pull/3973

No functional change

src/search.cpp

@@ -608,7 +608,6 @@ namespace {
     (ss+2)->killers[0]   = (ss+2)->killers[1] = MOVE_NONE;
     (ss+2)->cutoffCnt    = 0;
     ss->doubleExtensions = (ss-1)->doubleExtensions;
-    ss->depth            = depth;
     Square prevSq        = to_sq((ss-1)->currentMove);
 
     // Initialize statScore to zero for the grandchildren of the current position.
@@ -869,7 +868,6 @@ namespace {
 
         MovePicker mp(pos, ttMove, probCutBeta - ss->staticEval, depth - 3, &captureHistory);
         bool ttPv = ss->ttPv;
-        bool captureOrPromotion;
         ss->ttPv = false;
 
         while ((move = mp.next_move()) != MOVE_NONE)
@@ -877,11 +875,9 @@ namespace {
             {
                 assert(pos.capture(move) || promotion_type(move) == QUEEN);
 
-                captureOrPromotion = true;
-
                 ss->currentMove = move;
                 ss->continuationHistory = &thisThread->continuationHistory[ss->inCheck]
-                                                                          [captureOrPromotion]
+                                                                          [true]
                                                                           [pos.moved_piece(move)]
                                                                           [to_sq(move)];