Lingui fallback locale not working as intended

[p-galligan]

Describe the bug

If a locale is detected that we don't have a translation for, the translation IDs appear instead of the translation. Need to fix the fallback locale detection.

To reproduce

Steps to reproduce the behavior:

1. Set your browser's preferred language to one that we do not have a translation for
2. Go to DIMES
3. See error messages (site will not display properly)

Expected behavior

We'd expect to display English, which is our fallback locale.

Impact on your work

Does not impact RAC work, but would confuse researchers.

[p-galligan]

Closing. Fixed by #653