Remove conditional from user partial in favor of `User#display_name`
Remove conditional from user partial in favor of `User#display_name`

`User#name` already handles this logic in a cleanly overridable way. It's also a
bit nicer since it avoids repeated access and comparison on `#name` and `#user_key`.

The goal is: display a nice displayable name when its available; display the
`#user_key` as a fall back.

samvera/hyrax,samvera/hyrax,samvera/hyrax,samvera/hyrax