New review comment by kymnob on void-packages repository

https://github.com/void-linux/void-packages/pull/48638#discussion_r1485205184

Comment:
Usually the tag name is `commands` or `perfix-commands` in such cases. Looks like `_values` doesn't allow to specify tag name and always defaults to `values`. The context looks a bit messy too:

    tags in context :completion::complete:vkpurge:argument-1:
        values  (_values _vkpurge)
    tags in context :completion::complete:vkpurge:values:
        values  (_values _vkpurge)

```suggestion
		local subcommands=(
			'list:list removable kernel versions'
			'rm:remove removable kernel versions'
		)
		_describe -t commands 'subcommand' subcommands
```

`_values` calls `_describe` under the hood anyway.