[DOC] Aggregation support for Derived Fields

[mch2]

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.
With PR opensearch-project/OpenSearch#14618 we will be adding aggregation support for Derived Fields in the next release (now 2.17).

This is to update documentation to remove the restriction on aggregations and add information on which agg types are not supported. Any geo related aggregation, significant terms or text, and scripted metric aggs are not supported.

*Version: List the OpenSearch version to which this issue applies, e.g. 2.14, 2.12--2.14, or all.
2.17+

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