Hide @none language tag

I noticed that skohub-vocabs will render a "@none" language tag when some attributes where a lang-tag is expected do not contain them:

<img width="1162" height="217" alt="Image" src="https://github.com/user-attachments/assets/bd706fc5-1736-4aad-95a8-ac3081a2a422" />

My proposal would be to hide this from the UI.