RedshiftDatabaseMetaData.getSchemas(null, null) throws "schema "***" does not exist"

This is an intermittent issue in Trino CI. Redshift sometimes throws `schema "xxx" does not exist` error.
I don't think the method should throw an exception even if a schema is dropped concurrently.

```
Caused by: com.amazon.redshift.util.RedshiftException: ERROR: schema "xxx" does not exist
at com.amazon.redshift.core.v3.QueryExecutorImpl.receiveErrorResponse(QueryExecutorImpl.java:2648)
at com.amazon.redshift.core.v3.QueryExecutorImpl.processResultsOnThread(QueryExecutorImpl.java:2295)
at com.amazon.redshift.core.v3.QueryExecutorImpl.processResults(QueryExecutorImpl.java:1886)
at com.amazon.redshift.core.v3.QueryExecutorImpl.processResults(QueryExecutorImpl.java:1878)
at com.amazon.redshift.core.v3.QueryExecutorImpl.execute(QueryExecutorImpl.java:375)
at com.amazon.redshift.jdbc.RedshiftStatementImpl.executeInternal(RedshiftStatementImpl.java:519)
at com.amazon.redshift.jdbc.RedshiftStatementImpl.execute(RedshiftStatementImpl.java:440)
at com.amazon.redshift.jdbc.RedshiftStatementImpl.executeWithFlags(RedshiftStatementImpl.java:381)
at com.amazon.redshift.jdbc.RedshiftStatementImpl.executeCachedSql(RedshiftStatementImpl.java:367)
at com.amazon.redshift.jdbc.RedshiftStatementImpl.executeWithFlags(RedshiftStatementImpl.java:344)
at com.amazon.redshift.jdbc.RedshiftStatementImpl.executeQuery(RedshiftStatementImpl.java:268)
at com.amazon.redshift.jdbc.RedshiftDatabaseMetaData.getSchemas(RedshiftDatabaseMetaData.java:1999)
```

Start in RedshiftDatabaseMetaData.java at getSchemas(), around line 1999, and review how schema metadata queries handle schemas dropped during execution. Reproduce or inspect the Trino CI failure if possible; done means getSchemas(null, null) no longer propagates the concurrent schema-not-found error.

Written by the indexing model from the issue text.