Don't use TT just to save a node evaluation

In search(), after we evalute the position, in case there
isn't any TT entry we create one with just the evaluation
score.

This patches removes that code. The reason becuase the patch
deserves a single commit it is becuase introduces a (very small)
functional change due to the fact that the total number of
TT stores is less now and this slightly alters the TT hits
of our benchmark.

bench: 4983262

src/search.cpp

@@ -585,10 +585,6 @@ namespace {
                 || ((tte->type() & BOUND_UPPER) && ttValue < eval))
                 eval = ttValue;
         }
-
-        if (!tte)
-            TT.store(posKey, VALUE_NONE, BOUND_NONE, DEPTH_NONE, MOVE_NONE,
-                     ss->staticEval, ss->evalMargin);
     }
 
     // Update gain for the parent non-capture move given the static position