Update approximate-knn-search.md

[benwtrent]

related: https://github.com/elastic/elasticsearch/pull/123453/files

[john-wagster]

LGTM

Just to document something already discussed; I believe this used to be in ES under docs/reference/how-to not sure if that's intentional or not.

[leemthompo]

@john-wagster @benwtrent

Just to document something already discussed; I believe this used to be in ES under docs/reference/how-to not sure if that's intentional or not.

Just FYI that the new markdown files have mappings to their old 8.x asciidoc counterparts in the yaml frontmatter, for example for this file it's here, which is helpful.

Thanks for adapting and spreading the word about the docs changes, much appreciated :)