devise-two-factor gem is a blocker to Rails 7 upgrade
It relies on attr_entrypted gem that is not compatible
with Rails 7 newly introduced native encryption

Avoiding devise-two-factor gem dependency let us be
more flexible when it comes down to updating libraries
it currently rely on

It makes sense to gradually replace the gem with
custom code that simply uses rotp gem. It doesn't
require a lot more code to implement it this way

Changelog: changed