[email services] re-remove custom domain requirement from "Minimum to Qualify" (#3281)

Signed-off-by: pharaonic-faery <32229347+pharaonic-faery@users.noreply.github.com>

docs/email.md

@@ -277,7 +277,6 @@ We regard these features as important in order to provide a safe and optimal ser
 
 - Must encrypt email account data at rest with asymmetric encryption, where only the user has the private keys needed to decrypt it.
 - Must be capable of exporting emails as [Mbox](https://en.wikipedia.org/wiki/Mbox) or individual .EML with [RFC5322](https://datatracker.ietf.org/doc/rfc5322) standard.
-- Allow users to use their own [domain name](https://en.wikipedia.org/wiki/Domain_name). Custom domain names are important to users because it allows them to maintain their agency from the service, should it turn bad or be acquired by another company which doesn't prioritize privacy.
 - Must operate on owned infrastructure, i.e. not built upon third-party email service providers.
 
 **Best Case:**