Clarify wording of playlist protip

Per discussion on https://github.com/grafana/grafana/commit/154fbe2413f9abe33157baa563e42fbf67e2f27b#r31238888 it seemed like this wording might be easier to understand.

public/app/features/playlist/partials/playlists.html

@@ -59,7 +59,7 @@
       buttonIcon: 'fa fa-plus',
       buttonLink: 'playlists/create',
       buttonTitle: ' Create Playlist',
-      proTip: 'You can use playlists to remove control TVs',
+      proTip: 'You can use playlists to cycle dashboards on TVs without user control',
       proTipLink: 'http://docs.grafana.org/reference/playlist/',
       proTipLinkTitle: 'Learn more',
       proTipTarget: '_blank'