release-19.2: importccl: Disallow IMPORT INTO interleaved tables.

PR: https://github.com/cockroachdb/cockroach/pull/41651

From release notes:
> It is no longer possible to use [`IMPORT INTO`](../v19.2/import-into.html) with an interleaved table. This restriction is temporary and will be lifted in a future release. [#41651][#41651] {% comment %}doc{% endcomment %}