Remove unneeded & incorrect check.

the removed line is not needed, since with the conditions on SE, eval
equals ttValue (except inCheck), which must be larger than beta if the second condition
is true.

The removed line is also incorrect as eval might be VALUE_NONE at this
location if inCheck. This removal addresses part of https://github.com/official-stockfish/Stockfish/pull/2406#issuecomment-552642608

No functional change.

src/search.cpp

@@ -1033,8 +1033,7 @@ moves_loop: // When in check, search starts from here
           // search without the ttMove. So we assume this expected Cut-node is not singular,
           // that multiple moves fail high, and we can prune the whole subtree by returning
           // a soft bound.
-          else if (   eval >= beta
-                   && singularBeta >= beta)
+          else if (singularBeta >= beta)
               return singularBeta;
       }