Fix mount test

[Mount][mount]ing and [its test][test] still don't work.

[mount]: https://mojolicious.org/perldoc/Mojolicious/Plugin/Mount
[test]: https://github.com/memowe/contenticious/blob/637edeabeed48e9e487c1cdebd0c2b3d79acc165/t/07_mount.t#L3