[Internal]: Remove outdated suppression warning

[yctercero]

Description

With the introduction of prebuilt rule customization, users are now able to add alert suppression to prebuilt rules without the need of duplicating it. However, we didn't catch removing this warning when the feature (prebuilt rule customization) went out.

Resources

Docs link: https://www.elastic.co/docs/solutions/security/detect-and-alert/suppress-detection-alerts

Section:

Note
Alert suppression is not available for Elastic prebuilt rules. However, if you want to suppress alerts for a prebuilt rule, you can duplicate it, then configure alert suppression on the duplicated rule.

Which documentation set does this change impact?

Elastic On-Prem and Cloud (all)

Feature differences

What release is this request related to?

8.19+

Serverless release

Collaboration model

The documentation team

Point of contact.

Main contact: @yctercero

Stakeholders: @approksiu @banderror

[nastasha-solomon]

8.x, 9.x, and Serverless PRs have been merged.