Collapse inner hits rest test should not skip 5.x

Relates https://github.com/elastic/elasticsearch/pull/24517

rest-api-spec/src/main/resources/rest-api-spec/test/search/110_field_collapsing.yml

@@ -107,8 +107,8 @@ setup:
 "field collapsing and inner_hits":
 
   - skip:
-      version: " - 5.99.99"
-      reason:  disable this test temporary due to a pending backport (#24517)
+      version: " - 5.2.99"
+      reason:  this uses a new API that has been added in 5.3
 
   - do:
       search: