[DOCS] Documentation for rule `version` is outdated and for rule `revision` is missing

[banderror]

Epic: elastic/kibana#200310
Related to: #3116

Summary

The Update rule documentation page:

• Lists the version field among the optional request fields. This shouldn't be the case - we shouldn't allow users to set/change the version field via CRUD and other API endpoints. The version field is managed by the server internally and can only be changed by prebuilt rule authors in a rule's source file. Here, either the doc is outdated, or we need to fix this in the app and update the docs accordingly. This understanding is not correct anymore.
• States that If this is not provided, the rule’s version number is incremented by 1.. This is not the case anymore, because we changed the semantics of the version field, so now it tracks the version of the rule's source (content). We introduced a new field for the If this is not provided, the rule’s version number is incremented by 1. semantics, and it's called revision.

Any fixes in the app should not introduce breaking changes at the schema level (user sending a version in a request shouldn't get a 400 response).

All pages under https://www.elastic.co/guide/en/security/8.8/rule-api-overview.html that mention the version field should be updated.

Finally, the new rule revision field should be documented. Looks like it wasn't (fully?) done in #3116