♻️(backend) remove lazy from languages field on User model

The idea behind wrapping choices in `lazy` function was to allow
overriding the list of languages in tests with `override_settings`.
This was causing makemigrations to keep on including the field in
migrations when it is not needed. Since we finally don't override
the LANGUAGES setting in tests, we can remove it to fix the problem.

Taken from docs #c882f13

src/backend/core/models.py

@@ -14,7 +14,6 @@ from django.core import mail, validators
 from django.core.exceptions import PermissionDenied, ValidationError
 from django.db import models
 from django.utils import timezone
-from django.utils.functional import lazy
 from django.utils.text import capfirst, slugify
 from django.utils.translation import gettext_lazy as _
 
@@ -164,7 +163,7 @@ class User(AbstractBaseUser, BaseModel, auth_models.PermissionsMixin):
     )
     language = models.CharField(
         max_length=10,
-        choices=lazy(lambda: settings.LANGUAGES, tuple)(),
+        choices=settings.LANGUAGES,
         default=settings.LANGUAGE_CODE,
         verbose_name=_("language"),
         help_text=_("The language in which the user wants to see the interface."),