[Java][FlightRPC] Update benchmark to be on par with C++

[asfimport]

See apache/arrow#13980

The Java benchmark isn't comparable out of the box (and it seems like there's an unexplained gap between it and the C++ benchmark)

Reporter: David Li / @lidavidm

_{Note: This issue was originally created as ARROW-17537. Please see the migration documentation for further details.}