message: explain the need to enable async queries
diff: @@ -889,6 +889,9 @@ cache store when upgrading an existing environment.
  resulting in weird behaviors like duplicate delivery of reports,
  higher than expected load / traffic etc.
  +* SQL Lab will only run your queries asynchronously if you enable
  + "Asynchronous Query Execution" in your database settings.
  +
  Email Reports
  -------------
  