release-23.2.0-rc: concurrency: quieten KVNemesis failure because of validation

[blathers-crl]

Backport 1/1 commits from #116242 on behalf of @arulajmani.

/cc @cockroachdb/release

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We've seen KVNemesis fail regularly because of a specific validation error. For now, quieten the assertion until the issue is fixed -- this ensures legit bugs aren't drowned out by the noise.

Informs #115694
Informs #115598

Release note: None

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Release justification:

[blathers-crl]

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[blathers-crl]

It looks like your PR touches production code but doesn't add or edit any test code. Did you consider adding tests to your PR?

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[cockroach-teamcity]

This change is