API / Category / Fix update fields

Error was Validation Failed: 1: script or doc is missing.

Related to ES8 migration #7599

core/src/main/java/org/fao/geonet/kernel/search/EsSearchManager.java

@@ -365,7 +365,7 @@ public BulkResponse updateFields(String id, Map<String, Object> fieldMap, Set<St
         UpdateOperation addFieldRequestOperation = UpdateOperation.of(
             b -> b.id(id)
                 .index(defaultIndex)
-                .action(action -> action.upsert(fieldMap))
+                .action(action -> action.doc(fieldMap))
         );
 
         List<BulkOperation> bulkOperationList = new ArrayList<>();