Disable django.security.DisallowedHost from logging

[humitos]

We have properly configured our ALLOWED_HOST setting and it's blocking some of these attacks properly. Although, this is spamming Sentry with many error logs.

Since this is not an error and I think we don't really need to take any kind of action, we should disable this from the logging as mentioned here:

https://docs.djangoproject.com/en/1.11/topics/logging/#django-security

Sentry query: https://sentry.io/read-the-docs/readthedocs-org/?query=logger%3A%22django.security.DisallowedHost%22

[dojutsu-user]

@humitos
I would like to work on this issue.