Fix a call to ngettext, and update to use the new plugin capabilities.
Review Request #11022 — Created May 15, 2020 and submitted
During the admin UI rewrite, I forgot a parameter to
previously went unnoticed, but with our new babel-plugin-django-gettext,
it now becomes a build-time error.
This change fixes this up to provide the third argument, the count, and
at the same time switches to using the new syntax, simplifying the code
and reducing the setup for it.
Verified the generated code (when used against an upcoming build of
babel-plugin-django-gettext, which fixes ngettext-related issues).