Hide disabled language from list when editing content with translations.

Steps

1. Create several languages in Admin / Languages (and add them in ezplatform.yml).
2. Create an Article in main language.
3. Add translations to this Article in the other languages. (screen1)
4. Go to Admin / Languages and disable one of the languages. (screen2)
5. (optional) Go to Content / Content structure and start creating new content.
6. (optional) Verify available languages. (screen3)
7. Go to the Article in View mode and verify the list of languages in language switcher. (screen4)
8. Click Edit on the menu on the right side.
9. Verify the list of languages on the Select language pop-up.

Actual: Languages for all created translations are displayed. (screen5)
Expected: Disabled languages are hidden from this list.

Remarks: What is more user can edit in the disabled language (and create a draft).