Revert "Reduce more when improving and ttvalue is lower than alpha"

The patch regressed significantly at longer time controls.

Passed VLTC:
https://tests.stockfishchess.org/tests/view/6644c7a2bc537f5619453096
LLR: 2.95 (-2.94,2.94) <0.00,2.00>
Total: 43336 W: 11177 L: 10884 D: 21275
Ptnml(0-2): 3, 4432, 12507, 4721, 5

Passed VVLTC:
https://tests.stockfishchess.org/tests/view/66450c974aa4fa9a83b6d0b0
LLR: 2.95 (-2.94,2.94) <0.50,2.50>
Total: 32394 W: 8350 L: 8072 D: 15972
Ptnml(0-2): 2, 2798, 10317, 3080, 0

closes #5251

Bench: 1594188

src/search.cpp

@@ -1134,9 +1134,6 @@ Value Search::Worker::search(
         if (PvNode)
             r--;
 
-        if (improving && ttValue <= alpha && move != ttMove)
-            r++;
-
         // Increase reduction if next ply has a lot of fail high (~5 Elo)
         if ((ss + 1)->cutoffCnt > 3)
             r++;