Remove interface languagecode prefix in tags.

[aleene]

Happens in allergens, which should be translated.

IN packaging, it should be in the main product language, but for en: it is not removed.

[aleene]

The allergen thing is a synonym that is unknown to OFF, so I will add it there.

[aleene]

This is also an issue in the labels

[aleene]

The approach is now:

• edit the original tags (either remote or local);
• remove the main language prefix (if any) on display;
• when uploading writing add prefixes to all tags;