Absolute path literal so Home Manager does not fail when the Nix option
`lint-absolute-path-literals` is set to `fatal`.
The purpose of `makePath` was to avoid multiple slashes in the printed
path. This is unnecessary as can be seen by the discover entry which
does not do this "beautification".
Drop the dirty_path.nix test as it is no longer relevant.
Update the tests to the new output, which now contains a trailing slash.
This is fine as the khards path attribute expects an directory.
