[8.9] [DOCS] Fix authentication types for alerting rule enable API (elastic#171807) (elastic#172002)

# Backport

This will backport the following commits from `main` to `8.9`:
- [[DOCS] Fix authentication types for alerting rule enable API
(elastic#171807)](elastic#171807)

<!--- Backport version: 8.9.7 -->

### Questions ?
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Fix authentication types for alerting rule enable API
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Co-authored-by: Lisa Cawley <[email protected]>

Author: kibanamachine

docs/api/alerting/enable_rule.asciidoc

@@ -6,8 +6,6 @@
 
 Enable a rule.
 
-WARNING: This API supports <<token-api-authentication>> only.
-
 [NOTE]
 ====
 For the most up-to-date API details, refer to the