Clarify how to start a tutorial

https://meta.discourse.org/t/does-the-advanced-user-tutorial-still-exist/123661/14

plugins/discourse-narrative-bot/config/locales/server.en.yml

@@ -117,8 +117,8 @@ en:
         tracks: |-
           I currently know how to do the following things:
 
-          `@%{discobot_username} %{reset_trigger} %{default_track}`
-          > Starts one of the following interactive tutorials: %{tracks}.
+          `@%{discobot_username} %{reset_trigger} {name-of-tutorial}`
+          > Starts an interactive tutorial. `{name-of-tutorial}` can be one of: `%{tracks}`.
         bot_actions: |-
           `@%{discobot_username} %{dice_trigger} 2d6`
           > :game_die: 3, 6