Fix rest test skip version

multi_span prefix queries do not work with the prefix field
before 6.4.

Relates #31066

Author: jimczi

rest-api-spec/src/main/resources/rest-api-spec/test/search/190_index_prefix_search.yml

@@ -66,7 +66,7 @@ setup:
 ---
 "search index prefixes with span_multi":
   - skip:
-      version: " - 6.2.99"
+      version: " - 6.3.99"
       reason: span_multi throws an exception with prefix fields on < versions
 
   - do: