sql/backfill: TestVectorIndexWithPrefixBackfill failed

sql/backfill.TestVectorIndexWithPrefixBackfill [failed](https://mesolite.cluster.engflow.com/invocations/default/f45bd1d0-12b2-4ac1-8a11-fd02739b6bf5?testReportRun=2&testReportShard=1&testReportAttempt=1#targets-Ly9wa2cvc3FsL2JhY2tmaWxsOmJhY2tmaWxsX3Rlc3Q=) on master @ [e0e5cc0991aa42aa512f2d8394e31854c4a21008](https://github.com/cockroachdb/cockroach/commits/e0e5cc0991aa42aa512f2d8394e31854c4a21008):

```
=== RUN TestVectorIndexWithPrefixBackfill
test_log_scope.go:172: test logs captured to: outputs.zip/logTestVectorIndexWithPrefixBackfill475238455
test_log_scope.go:82: use -show-logs to present logs inline
test_server_shim.go:168: automatically injected an external process virtual cluster under test; see comment at top of test_server_shim.go for details.
```

Parameters:
- attempt=1
- race=true
- run=2
- shard=1
Help

See also: [How To Investigate a Go Test Failure \(internal\)](https://cockroachlabs.atlassian.net/l/c/HgfXfJgM)

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Jira issue: CRDB-65436