Fix test for changed message

Message is only changed in 5.2.0 so we shouldn't assert on it
if we're running with any nodes less than that version.

rest-api-spec/src/main/resources/rest-api-spec/test/tasks.get/10_basic.yaml

@@ -1,5 +1,8 @@
 ---
 "get task test":
+  - skip:
+      version: " - 5.1.99"
+      reason: massage was changed in 5.2.0
   # Note that this gets much better testing in reindex's tests because it actually saves the task
   - do:
       cluster.state: {}