Update validators.py

[jchauhan-building-engines]

Fix: for Django 4 import issue with translation.

[blag]

Relevant bullet point from Django 4.0 changelog:

Features removed in 4.0

These features have reached the end of their deprecation cycle and are removed in Django 4.0.

• ...
• django.utils.translation.ugettext(), ugettext_lazy(), ugettext_noop(), ungettext(), and ungettext_lazy() are removed.