DOCS-1336 - Enable threat intel C2Cs

[jpipkin1]

Purpose of this pull request

This pull request adds notes stating that threat intel cloud-to-cloud sources are automatically installed for Cloud SIEM customers.

Select the type of change

• Minor Changes - Typos, formatting, slight revisions
• Update Content - Revisions, updating sections
• New Content - New features, sections, pages, tutorials
• Site and Tools - .clabot, version updates, maintenance, dependencies, new packages for the site (Docusaurus, Gatsby, React, etc.)

Ticket (if applicable)

DOCS-1336

[jpipkin1]

Closing this PR because it turns out that no documentation is needed for the feature.