[7.x] Update ILM node attributes blacklist. (#62093) (#62191)

- Remove 'testattr' because this doesn't seem to be used in production by ES.
- Add 'transform.node' (added via https://github.com/elastic/elasticsearch/pull/52712/files#diff-225cc2c1291b4c60a8c3412a619094e1R147).

x-pack/legacy/plugins/index_lifecycle_management/server/routes/api/nodes/constants.ts

@@ -8,6 +8,8 @@ export const NODE_ATTRS_KEYS_TO_IGNORE: string[] = [
   'ml.enabled',
   'ml.machine_memory',
   'ml.max_open_jobs',
-  'testattr',
+  // Used by ML to identify nodes that have transform enabled:
+  // https://github.com/elastic/elasticsearch/pull/52712/files#diff-225cc2c1291b4c60a8c3412a619094e1R147
+  'transform.node',
   'xpack.installed',
 ];