chore: Remove self-update from default crate features

[alerque]

The self-updater feature is problematic for distro package builders where the executable does not have permission and should not be trying to monkey with the system installed binaries. Distros have their own update mechanisms that shouldn't be tampered with by every app that comes along. This means distro have to build with --no-default-features for apps that include self-updaters by default, but that also means we have to maintain a list of features we do want. This is not only tedious it is error-prone because there is a very good chance of new features getting overlooked when doing version bumps.

Setting up a feature group like this makes it much easier for distros to build without the unwanted features without getting out of sync with upstream enhancements over time.