Commit 798f85a710 changed the way the languages menu is generated in
order to improve the items' descriptions. This revealed that items in
`bpy.app.translations.locales` used this description instead of the
identifier, resulting in them looking like:
'Locale code: ca_AD. Translation progress: 100%'
instead of:
'ca_AD'
To use the language code, this commit uses the menu item's identifier
instead of description.
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This should be backported to 4.5.
Pull Request: https://projects.blender.org/blender/blender/pulls/144366