There is no need to clear TT at allocation time

Operator new() already returns a zeroed memory.

No functional change.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>

src/tt.cpp

@@ -72,7 +72,6 @@ void TranspositionTable::set_size(size_t mbSize) {
                     << " MB for transposition table." << std::endl;
           Application::exit_with_failure();
       }
-      clear();
   }
 }