document accept_enterprise parameter (#79012) (#79256)

* document accept_enterprise parameter

This was added in 7.6, will be deprecated in 8.x, and removed in 9.x+ (noted in text).

https://github.com/elastic/elasticsearch/pull/50067

* Update wording and deprecation notice

* Incorporate review feedback

Co-authored-by: Adam Locke <adam.locke@elastic.co>

Co-authored-by: Ken MacInnis <ken.macinnis@elastic.co>

docs/reference/licensing/get-license.asciidoc

@@ -32,7 +32,14 @@ response after cluster startup, wait a short period and retry the request.
 `local`::
   (Boolean) Specifies whether to retrieve local information. The default value
   is `false`, which means the information is retrieved from the master node.
-
+  
+ `accept_enterprise`::
+(Boolean) If `true`, this parameter returns `enterprise` for Enterprise
+license types. If `false`, this parameter returns `platinum` for both
+`platinum` and `enterprise` license types. This behavior is maintained for
+backwards compatibility.
+   
+deprecated::[7.6.0,"This parameter is deprecated and will always be set to `true` in 8.x."]
 
 [discrete]
 ==== Authorization