Docs: Clarifies from which version the Patch VERB is available (#17532)

* Docs: Clarifies from which version the Patch VERB is available

Closes: #17508

* Docs: Removes setting after PR comments

docs/sources/http_api/annotations.md

@@ -195,6 +195,7 @@ Content-Type: application/json
 ```
 
 ## Patch Annotation
+> This is available in Grafana 6.0.0-beta2 and above.
 
 `PATCH /api/annotations/:id`