uninstall: better example in dependency warning

Previously, this only included a subset of all the kegs the user was
trying to uninstall. With this change, all named formulae/kegs will be
included in the example command.

Library/Homebrew/cmd/uninstall.rb

@@ -121,7 +121,7 @@ module Homebrew
     end
 
     def sample_command
-      "brew uninstall --ignore-dependencies #{list reqs.map(&:name)}"
+      "brew uninstall --ignore-dependencies #{list ARGV.named}"
     end
 
     def are_required_by_deps