Remove django-allauth-2fa

[matmair]

We are currently using the awesome django-allauth-2fa. The upstream project django-allauth has added mfa recently and seems to support pretty much everything django-allauth does so IMO it is time to reduce the depency tree and remove django-allauth-2fa.

There are actually docs for this: https://docs.allauth.org/en/latest/mfa/django-allauth-2fa.html.
Although it should not really be breaking, I would still consider it as such as this is probably a one-way street.

[matmair]

A few issues are linked to 2fa and it is probalby simpler to first do this and then tackle them: #6200, #6132

Also it seems that django-allauth could gain more factors so it is probably a safer bet long term:
pennersr/django-allauth#3550

[SchrodingersGat]

I'm on board with this - makes sense to use a single library rather than maintaining two dependencies. I am also keen to address this soon so we can tackle the other outstanding issues

[matmair]

The release of 0.14.0 is nearing, moving to the next milestone