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GH-35316: [C++][FlightSQL] Use RowsToBatches() instead of ArrayFromJSON() in SQLite example server (#35322)

### Rationale for this change

`ArrayFromJSON()` requires `libarrow_testing.so`. But `cpp/examples/arrow/flight_sql_example.cc` uses the SQLite example server without `libarrow_testing.so` dependency.

### What changes are included in this PR?

Use `RowsToBatches()` in `libarrow.so` instead of `ArrayFromJSON()`.

### Are these changes tested?

Yes by hand.

### Are there any user-facing changes?

Yes.
* Closes: #35316

Authored-by: Sutou Kouhei <kou@clear-code.com>
Signed-off-by: Sutou Kouhei <kou@clear-code.com>