release-23.1: sql: avoid slow lock verification in TestSchemaChangeAfterCreateInTxn

[blathers-crl]

Backport 1/1 commits from #126114 on behalf of @rafiss.

/cc @cockroachdb/release

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The addition of test-only verification pushed this test over the timeout sometimes, such that running it under the deadlock detector would cause spurious failures. We avoid this by making the test smaller under deadlock, like we do for race builds.

fixes #126075
Release justification: test only change
Release note: None

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Release justification:

[blathers-crl]

Thanks for opening a backport.

Please check the backport criteria before merging:

• Backports should only be created for serious
  issues or test-only changes.
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[cockroach-teamcity]

This change is 

[Dedej-Bergin]

Reviewable status: complete! 1 of 0 LGTMs obtained (waiting on @fqazi)