Fix JsonExprBenchmark.cpp (facebookincubator#9574)

Summary:
Pull Request resolved: facebookincubator#9574

Benchmark used to fail because it didn't initialize memory manager.

Reviewed By: xiaoxmeng

Differential Revision: D56452087

fbshipit-source-id: b564b457728b0efff49e2b72c3aed5aa99dedd1d

velox/functions/prestosql/benchmarks/JsonExprBenchmark.cpp

@@ -475,6 +475,9 @@ BENCHMARK_DRAW_LINE();
 
 int main(int argc, char** argv) {
   folly::Init init{&argc, &argv};
+
+  facebook::velox::memory::MemoryManager::initialize({});
+
   folly::runBenchmarks();
   return 0;
 }