Added -end usecase for Sky Drop
Added -end usecase for Sky Drop

Added message for when a Pokemon is freed from Sky Drop (due to Gravity or
the Sky Drop user fainting) in preparation for Sky Drop refactor coming in
later.

Zarel/Pokemon-Showdown-Client,QuiteQuiet/Pokemon-Showdown-Client,submindraikou/Pokemon-Showdown-Client,asgdf/Pokemon-Showdown-Client,Zarel/Pokemon-Showdown-Client,sirDonovan/Pokemon-Showdown-Client,QuiteQuiet/Pokemon-Showdown-Client,QuiteQuiet/Pokemon-Showdown-Client,Zarel/Pokemon-Showdown-Client,panpawn/Gold-Client,Zarel/Pokemon-Showdown-Client,sirDonovan/Pokemon-Showdown-Client,QuiteQuiet/Pokemon-Showdown-Client,panpawn/Gold-Client,asgdf/Pokemon-Showdown-Client,submindraikou/Pokemon-Showdown-Client,asgdf/Pokemon-Showdown-Client,asgdf/Pokemon-Showdown-Client,sirDonovan/Pokemon-Showdown-Client,submindraikou/Pokemon-Showdown-Client,panpawn/Gold-Client,sirDonovan/Pokemon-Showdown-Client