Describe the bug
When a users admin language is different from the default site language, the Categories and Tags meta box title in the Gutenberg editor sidebar initially show in the users admin language but as soon as one is clicked to open the meta box, the title will jump to the default site language.

The same thing happens with custom taxonomies, but other meta boxes, like Featured Image, do not suffer this issue. Also the taxonomy meta box content remains in the user admin language. Only the title changes. See screen shots before and after.

Gutenberg 3.4.0

To Reproduce
Steps to reproduce the behavior:

1. Set a different language (than the general site language) in your user Profile
2. Edit a post and see that the taxonomy meta boxes have titles in the alternative language set above
3. Now click on any taxonomy meta box title to toggle open/close
4. Notice that the title switches to the site default language

Expected behavior
Meta boxes keep their user admin language.

Screenshots
Before toggling the meta boxes, titles are English (user admin language) :

After toggling, taxonomy titles switched to French (site language) :

Desktop (please complete the following information):

• OS: Linux
• Google Chrome 68.0.3440.84