GH-35144: [C++] Fix a unit test broken when the output order of the aggregate node changed

[westonpace]

Rationale for this change

The unit test was broken by a recent change and needed to be updated.

What changes are included in this PR?

The unit test has been updated to expect the correct order.

Are these changes tested?

Yes

Are there any user-facing changes?

No

• Closes: [C++] Unit test regression introduced by #34931 #35144

[github-actions]

• Closes: [C++] Unit test regression introduced by #34931 #35144

[github-actions]

⚠️ GitHub issue #35144 has been automatically assigned in GitHub to PR creator.

[icexelloss]

Thanks @westonpace - I found the same issue. I thought all tests passed before I merged it but I must have missed somehow. Thanks for fixing!

[westonpace]

I thought all tests passed before I merged it but I must have missed somehow.

They probably did all pass but they ran before #34904 was merged in. This kind of thing happens every so often when two PRs conflict with each other.

[ursabot]

Benchmark runs are scheduled for baseline = 2ba6628 and contender = d4f7332. d4f7332 is a master commit associated with this PR. Results will be available as each benchmark for each run completes.
Conbench compare runs links:
[Finished ⬇️0.0% ⬆️0.0%] ec2-t3-xlarge-us-east-2
[Failed] test-mac-arm
[Finished ⬇️0.0% ⬆️0.0%] ursa-i9-9960x
[Finished ⬇️0.34% ⬆️0.0%] ursa-thinkcentre-m75q
Buildkite builds:
[Finished] d4f73322 ec2-t3-xlarge-us-east-2
[Failed] d4f73322 test-mac-arm
[Finished] d4f73322 ursa-i9-9960x
[Finished] d4f73322 ursa-thinkcentre-m75q
[Finished] 2ba66285 ec2-t3-xlarge-us-east-2
[Failed] 2ba66285 test-mac-arm
[Finished] 2ba66285 ursa-i9-9960x
[Finished] 2ba66285 ursa-thinkcentre-m75q
Supported benchmarks:
ec2-t3-xlarge-us-east-2: Supported benchmark langs: Python, R. Runs only benchmarks with cloud = True
test-mac-arm: Supported benchmark langs: C++, Python, R
ursa-i9-9960x: Supported benchmark langs: Python, R, JavaScript
ursa-thinkcentre-m75q: Supported benchmark langs: C++, Java