darklore

Use cobra builtin completion command

5

Latest `spf13/cobra` has zsh-completion support, and has `completion` subcommand by default. This PR upgrade `spf13/cobra` and use these supports.

coursier: add shell completions

1

- [x] Have you followed the [guidelines for contributing](https://github.com/Homebrew/homebrew-core/blob/HEAD/CONTRIBUTING.md)? - [x] Have you ensured that your commits follow the [commit style guide](https://docs.brew.sh/Formula-Cookbook#commit)? - [x] Have you checked that there aren't...

- Installs bash completion script in addition to zsh completion when installed by homebrew. - Change option name to avoid the installation from "--without-zsh-completions" to "--without-shell-completions"