Update limitations on 'dense_vector' field type support

[carlosdelest]

Clarify the support status of the 'dense_vector' field type in ESQL queries.

[elasticsearchmachine]

Pinging @elastic/es-search-relevance (Team:Search Relevance)

[elasticsearchmachine]

Pinging @elastic/core-docs (Team:Docs)

[github-actions]

🔍 Preview links for changed docs

• docs/reference/query-languages/esql/limitations.md

[github-actions]

ℹ️ Important: Docs version tagging

👋 Thanks for updating the docs! Just a friendly reminder that our docs are now cumulative. This means all 9.x versions are documented on the same page and published off of the main branch, instead of creating separate pages for each minor version.

We use applies_to tags to mark version-specific features and changes.

Expand for a quick overview

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✅ At the page level to indicate which products/deployments the content applies to (mandatory)
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• Check out the cumulative docs guidelines
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