Checks framework complains about unapplied migrations when running `manage.py migrate`

[Baptiste Mispelon]

Suppose you've created a new application with some models and you've subsequently run manage.py makemigrations.

The next step is to run manage.py migrate.

When you do that, the first thing that you see is the checks framework telling you that you have unapplied migrations and that you should run manage.py migrate.

That doesn't seem very helpful and I think it'd be better in this case to not output anything.

[Marc Tamlyn]

This is effectively a duplicate of #21856 - this warning should not be part of the checks framework.