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MINOR: [C++][FlightRPC] Add missing app_metadata arguments (#38548)



### Rationale for this change

This issue was discovered in the #38210 issue. It is reproduced on Mac with ARM Architecture CPU (**M1**). If the argument for `app_metadata` is not explicitly added, the build fails.

### What changes are included in this PR?

* Added the argument for `app_metadata` explicitly

### Are these changes tested?

Yes (Build)

### Are there any user-facing changes?

No

Authored-by: Hyunseok Seo <hsseo0501@gmail.com>
Signed-off-by: David Li <li.davidm96@gmail.com>