release-25.2: logictest: skip distsql_numtables under race

[yuzefovich]

Backport 1/1 commits from #160397 on behalf of @yuzefovich.

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We've seen a timeout in this test twice under race with no clear signs of things going wrong, other than the cluster being overloaded - it uses 5node config, so let's just skip it under race.

Fixes: #160391.
Release note: None

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Release justification: test-only change.

[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 #160412 is compliant with backport policy

Confidence: high
Backward compatible: true
Explanation: The PR is compliant with the backport policy for the following reasons: 1. The PR marks a change that affects only test or non-production code, specifically within a logic test file matching the non-production file patterns (as it includes '*/testdata/' in the path). 2. The PR body explicitly includes a 'Release justification: test-only change', which directly exempts it from the standard backport policy requirements. 3. The PR is involved with skipping a test that's causing timeouts under specific conditions (race), which is an appropriate adjustment for ensuring test reliability without impacting production code.

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[cockroach-teamcity]

This change is