Update monitoring-kibana.json (#40899)

Author: Bamieh

x-pack/plugin/core/src/main/resources/monitoring-kibana.json

@@ -50,6 +50,13 @@
  },
  "kibana_stats": {
  "properties": {
+ "usage": {
+ "properties": {
+ "index": {
+ "type": "keyword"
+ }
+ }
+ },
  "kibana": {
  "properties": {
  "uuid": {