Deletes the given dependencies’ files, including build artifacts and fetched sources.

Since this is a destructive action, cleaning of dependencies can only happen by passing arguments/options:

• dep1, dep2 - the name of dependencies to be deleted
• --all - deletes all dependencies
• --unused - deletes only unused dependencies (no longer mentioned in the mix.exs file)
• --unlock - also unlocks the deleted dependencies

By default this task works across all environments, unless --only is given.