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MINOR: [Go] Tweak Flight SQL demo server for ADBC Java Flight SQL (#34776)



### Rationale for this change

The ADBC Flight SQL driver/test suite depends on semantic error codes from the server.

### What changes are included in this PR?

Return a more specific error in the SQLite Flight SQL example server.

### Are these changes tested?

Yes

### Are there any user-facing changes?

No

Authored-by: David Li <li.davidm96@gmail.com>
Signed-off-by: Matt Topol <zotthewizard@gmail.com>