release-24.1: changefeedccl: fix reversed args for containment check in test logic

[blathers-crl]

Backport 1/1 commits from #152880 on behalf of @nicktrav.

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Fix a testing bug introduced in #131545 where the Contains check arguments were reversed. The error string being searched should precede the string being searched for. The examples from the API docs:

//	require.Contains(t, "Hello World", "World")
//	require.Contains(t, ["Hello", "World"], "World")
//	require.Contains(t, {"Hello": "World"}, "Hello")

Release note: None

Epic: None

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Release justification: Test only.

[blathers-crl]

Thanks for opening a backport.

Before merging, please confirm that it falls into one of the following categories (select one):

• Non-production code changes. Includes test-only changes, build system changes, etc.
• Fixes for serious issues. Defined in the policy as correctness, stability, or security issues, data corruption/loss, significant performance regressions, breaking working and widely used functionality, or an inability to detect and debug production issues.
• Other approved changes. These changes must be gated behind a disabled-by-default feature flag unless there is a strong justification not to.

Add a brief release justification to the PR description explaining your selection.

Also, confirm that the change does not break backward compatibility and complies with all aspects of the backport policy.

All backports must be reviewed by the TL and EM for the owning area.

[blathers-crl]

✅ PR #153208 is compliant with backport policy

Confidence: high
Backward compatible: true
Explanation: The pull request is compliant with the CockroachDB backport policy as it only includes changes to a test file (errors_test.go). Based on the file pattern, this is a non-production file focused specifically on testing functionality related to the changefeed. The policy states that changes affecting only non-production code, tests, or development tools are exempt from the requirements for critical bug justification or feature flag gating.

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[cockroach-teamcity]

This change is 

[nicktrav]

TFTR!