Remove packages that have issues disabled

That means there's no place for users to report bugs.

Excluded are oh-my-fish packages, presumably people can report bugs in
them to oh-my-fish.

packages/artisan

-type = plugin
-repository = https://github.com/james2doyle/omf-plugin-artisan
-maintainer = james2doyle
-description = Laravel artisan completions

packages/barracuda

-type = theme
-repository = https://github.com/meverss/barracuda
-maintainer = Marvin Eversley Silva <meverss@outlook.com>
-description = A fork of budspencer theme.

packages/bongnoster

-type = theme
-repository = https://github.com/kfkonrad/bongnoster-fish-theme
-description = A more slender adaption of the agnoster theme that displays the current user, path and VCS information
-maintainer = Kevin F. Konrad <info@kevinkonrad.de>

packages/keychain

-type = plugin
-repository = https://github.com/jitakirin/pkg-keychain.git
-maintainer = jitakirin <jitakirin@gmail.com>
-description = Keychain helps you manage SSH and GPG keys