[DOC] Reload certificates documentation

[Naarcha-AWS]

What do you want to do?

• Request a change to existing documentation
• Add new documentation
• Report a technical problem with the documentation
• Other

Tell us about your request. Provide a summary of the request.

Add documentation for the Reload Certificates API. If this API exists in the API spec, it will be added as part of issue #9050.

Version: List the OpenSearch version to which this issue applies, e.g. 2.14, 2.12--2.14, or all.

What other resources are available? Provide links to related issues, POCs, steps for testing, etc.

Relates to PR #9103. After publication of that PR, loop back around and add the link.