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GH-34743: [Python] Relax condition in flaky Flight test (#34747)

### Rationale for this change
This test is consistently flaky on AMD64 macOS.

### What changes are included in this PR?

Relax the test condition a bit.
### Are these changes tested?

This is a change to a test.

### Are there any user-facing changes?

No.
* Closes: #34743

Authored-by: David Li <li.davidm96@gmail.com>
Signed-off-by: Will Jones <willjones127@gmail.com>