Email announcements user is unclear/wrong

[mattcaswell]

HOWTO-publish-a-release says this about sending email announcements:

They
should be sent from the account of the person that owns the key used for
signing the release announcement

But, the email announcements are now signed by the team key (openssl-security/openssl-omc). It's unclear which user account needs to be used.

Sending from the wrong user account means that the gpg signatures will fail to verify in some email clients.