Always re-enable NNUE after "bench".

Restore the default NNUE setting (enabled) after a bench command.
This also makes the resulting program settings independent of the
number of FENs that are being benched.

Fixes issue #3112.

closes https://github.com/official-stockfish/Stockfish/pull/3113

No functional change.

src/benchmark.cpp

@@ -164,5 +164,7 @@ vector<string> setup_bench(const Position& current, istream& is) {
           ++posCounter;
       }
 
+  list.emplace_back("setoption name Use NNUE value true");
+
   return list;
 }