[Issue]: Move APIs to reference

[KOTungseth]

Type of issue

Inaccurate

What documentation page is affected

https://www.elastic.co/docs/explore-analyze/machine-learning/anomaly-detection/ml-api-quickref

What happened?

APIs are considered reference content and this page should be moved the reference section.

Additional info

No response

[shainaraskas]

this is a quick reference which is intended to tie the reference and narrative content together, so we might want to keep it