missing app when `needsApp` help could be more helpful

[ransombriggs]

-> % heroku cassandra
 ▸    Error: No app specified
 ▸    Usage: heroku cassandra:cqlsh [CLUSTER] --app APP
 ▸    We don't know which app to run this on.
 ▸    Run this command from inside an app folder or specify which app to use with --app APP
 ▸    
 ▸    https://devcenter.heroku.com/articles/using-the-cli#app-commands

vs

-> % heroku cassandra        
 ▸    No app specified