Remove convenience imports in django/core/mail/__init__.py

[Danic]

I found the following comment in django\core\mail\init.py

# Imported for backwards compatibility and for the sake
# of a cleaner namespace. These symbols used to be in
# django/core/mail.py before the introduction of email
# backends and the subsequent reorganization (See #10355)

#10355 relates to Django 1. As it's out of support, it maybe doesn't make sense to keep the backwards compatibility. Would it make sense to have a look at that file and check what of the code can be removed or if the comment should be updated?

[David Sanders]

I don't think we should remove these imports for a couple of reasons:

1. Some of them are documented as being imported from django.core.mail, eg SafeMIMEText here: ​https://docs.djangoproject.com/en/5.0/topics/email/#emailmessage-objects
2. There's no real harm in having some default imports? 🤔

If anything maybe we could remove the comment? 🤔

[Tim Graham]

The imports and comment look fine to me.