This test depended on system locale. It always failed with `LANG=fr_FR make test-frontend` and always passed with `LANG=C make test-frontend`.
- prevent this dependency by explicitly passing 'en-US'
- avoid process.env.TZ boilerplate with vi.stubEnv
Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/6649
Reviewed-by: Gusted <gusted@noreply.codeberg.org>
Reviewed-by: Beowulf <beowulf@beocode.eu>
a40284bec4