Remove killer move conditions from LMR

STC:
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 8459 W: 1619 L: 1477 D: 5363

LTC:
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 32239 W: 4404 L: 4299 D: 23536

Bench: 7597031

Resolves #534

src/search.cpp

@@ -982,9 +982,7 @@ namespace {
       // re-searched at full depth.
       if (    depth >= 3 * ONE_PLY
           &&  moveCount > 1
-          && !captureOrPromotion
-          &&  move != ss->killers[0]
-          &&  move != ss->killers[1])
+          && !captureOrPromotion)
       {
           ss->reduction = reduction<PvNode>(improving, depth, moveCount);