Mute failing test

Author: alexey-ivanov-es

x-pack/qa/rolling-upgrade/src/test/resources/rest-api-spec/test/upgraded_cluster/80_transform_jobs_crud.yml

@@ -225,6 +225,9 @@ setup:
         transform_id: "old-simple-continuous-transform"
 ---
 "Test GET, mixed continuous transforms":
+  - skip:
+      awaits_fix: "https://github.com/elastic/ml-team/issues/1522"
+      reason: "Transform system index migration is broken"
   - do:
       transform.get_transform:
         transform_id: "mixed-simple-continuous-transform"