[Telemetry] Remove custom code for spaces in telemetry (#27903) (#28175)

* Remove custom code for spaces in telemetry

* Undo this change

* Change how this is inserted into the monitoring doc

x-pack/plugins/spaces/server/lib/get_spaces_usage_collector.ts

@@ -70,9 +70,7 @@ export function getSpacesUsageCollector(server: any) {
         type: KIBANA_STATS_TYPE_MONITORING,
         payload: {
           usage: {
-            xpack: {
-              spaces: result,
-            },
+            spaces: result,
           },
         },
       };