Update 6-subscriptions.md
Update 6-subscriptions.md

Removed the where filter from the subscriptions, to prevent confusion when working on the tutorial, as they are not currently working.

Added a Note explaining this to people following the tutorial
howtographql/howtographql,howtographql/howtographql,howtographql/howtographql,DevanB/howtographql,DevanB/howtographql