[BUG][Detections] Clarify 7.x privileges required to prevent creation/modification of Detection Rules

[spong]

Description

Was working with @octavioranieri on determining the required privileges to make Rules read-only, and we noticed that the 7.x docs say that the Kibana space privileges should be All for the Security feature instead of Read. This appears to have been corrected in 8.0, and so only needs to be updated in the 7.x docs. The privileges docs were overhauled in 7.13, and so ideally this should be backported all the way to that release.

For the Manage alerts action of

8.0 Docs

7.13 -> 7.17 Docs

Relavant links:
PR that removed the need for Saved Object Management privileges in 7.12: elastic/kibana#90895

[jmikell821]

Merged #1685.