Automatic Import - 9.0 CEL features were back-ported to 8.18 docs

[rseldner]

The 8.18 Automatic Import documentation contains this note on CEL that applies to 9.x

When you select API (CEL input) as one of the sources, you will be prompted to provide the associated OpenAPI specification (OAS) file to generate a CEL program that consumes this API.
Source: https://www.elastic.co/guide/en/security/8.18/automatic-import.html

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9.0 docs: https://www.elastic.co/docs/solutions/security/get-started/automatic-import
Relevant 9.0 PRs with aligning with the note in question:

• [Automatic Import] Update CEL flow to UX design kibana#206491
• [Automatic Import] Migrating to UX design and adding support for generating auth kibana#202587

These PRs are not back-ported to 8.18 branch.