Fix test assertion

Author: tristanlabelle

app/backend/src/tests/test_i18n.py

@@ -47,4 +47,4 @@ def test_babel_locales():
             Locale(locale.replace("-", "_"))
         except UnknownLocaleError:
             unknown_locales.add(locale)
-    assert unknown_locales == {}
+    assert unknown_locales == set()