Docs enhancement: added reference to cluster-level setting search.default_allow_partial_results (#32810)

Closes #32809

Author: markharwood

docs/reference/search/request-body.asciidoc

@@ -90,7 +90,8 @@ And here is a sample response:
 
     Set to `false` to return an overall failure if the request would produce partial 
     results. Defaults to true, which will allow partial results in the case of timeouts
-    or partial failures.
+    or partial failures. This default can be controlled using the cluster-level setting
+    `search.default_allow_partial_results`.
 
 `terminate_after`::
 

docs/reference/search/uri-request.asciidoc

@@ -125,5 +125,6 @@ more details on the different types of search that can be performed.
 
 |`allow_partial_search_results` |Set to `false` to return an overall failure if the request would produce
 partial results. Defaults to true, which will allow partial results in the case of timeouts
-or partial failures..
+or partial failures. This default can be controlled using the cluster-level setting
+`search.default_allow_partial_results`.
 |=======================================================================