Doc: Clarify the impact of the aggregation leak (#80682)

* Clarifying the impact of the aggregation leak

* Update 7.15.asciidoc

Added transforms impact.

Author: ppf2

docs/reference/release-notes/7.15.asciidoc

@@ -17,6 +17,10 @@ Authorization::
 Aggregations::
 * Possible source of leaked delayable writables {es-pull}80166[#80166]
 
+NOTE: This issue only arises when using <<search-search-api-query-params,allow_partial_search_results=false>> 
+(e.g. <<transform-overview,transforms>>) on a search with aggregations AND if one of the underlying 
+shard level search requests fail. Kibana uses `allow_partial_search_results=true` (Elasticsearch default).
+
 Authorization::
 * Marking operator user no longer depends on license state {es-pull}79595[#79595]
 * Preserve request headers in a mixed version cluster {es-pull}79412[#79412] (issue: {es-issue}79354[#79354])