[8.9] [DOCS] Remove OAS API previews (elastic#168761) (elastic#169141)

# Backport

This will backport the following commits from `main` to `8.9`:
- [[DOCS] Remove OAS API previews
(elastic#168761)](elastic#168761)

<!--- Backport version: 8.9.8 -->

### Questions ?
Please refer to the [Backport tool
documentation](https://github.com/sqren/backport)

<!--BACKPORT [{"author":{"name":"Lisa
Cawley","email":"[email protected]"},"sourceCommit":{"committedDate":"2023-10-17T14:49:23Z","message":"[DOCS]
Remove OAS API previews
(elastic#168761)","sha":"382e3f6ec245aec89d52b4a4be1b8c5612c011c5","branchLabelMapping":{"^v8.12.0$":"main","^v(\\d+).(\\d+).\\d+$":"$1.$2"}},"sourcePullRequest":{"labels":["Team:Docs","release_note:skip","docs","backport:all-open","v8.6.3","v8.11.0","v8.12.0"],"number":168761,"url":"https://github.com/elastic/kibana/pull/168761","mergeCommit":{"message":"[DOCS]
Remove OAS API previews
(elastic#168761)","sha":"382e3f6ec245aec89d52b4a4be1b8c5612c011c5"}},"sourceBranch":"main","suggestedTargetBranches":["8.6"],"targetPullRequestStates":[{"branch":"8.6","label":"v8.6.3","labelRegex":"^v(\\d+).(\\d+).\\d+$","isSourceBranch":false,"state":"NOT_CREATED"},{"branch":"8.11","label":"v8.11.0","labelRegex":"^v(\\d+).(\\d+).\\d+$","isSourceBranch":false,"url":"https://github.com/elastic/kibana/pull/169124","number":169124,"state":"MERGED","mergeCommit":{"sha":"ac6ad7878db93ffa1aa5946196f6cf6bbb4af854","message":"[8.11]
[DOCS] Remove OAS API previews (elastic#168761)
(elastic#169124)"}},{"branch":"main","label":"v8.12.0","labelRegex":"^v8.12.0$","isSourceBranch":true,"state":"MERGED","url":"https://github.com/elastic/kibana/pull/168761","number":168761,"mergeCommit":{"message":"[DOCS]
Remove OAS API previews
(elastic#168761)","sha":"382e3f6ec245aec89d52b4a4be1b8c5612c011c5"}}]}]
BACKPORT-->

Author: lcawl