Use gettext_lazy in Django 2.0+ (ugettext_lazy is deprecated)

[bsolomon1124]

ugettext() is an alias for gettext() since Django 2.0 and is deprecated as of Django 3.0.

Avoid deprecation warning:

RemovedInDjango40Warning: django.utils.translation.ugettext_lazy() is deprecated in favor of django.utils.translation.gettext_lazy()

Ref:

• https://docs.djangoproject.com/en/3.1/releases/3.0/#features-deprecated-in-3-0
• https://github.com/django/django/blob/2b443cb6c2d55669b20019f2755c0711c3d23050/django/utils/translation/__init__.py#L139

[vstoykov]

Thank you for your contribution!