remove Email::Address dependency

remove Email::Address dependency

git has stricter requirements for ident names (no '<>')
which Email::Address allows.

Even in 1.908, Email::Address also has an incomplete fix for
CVE-2015-7686 with a DoS-able regexp for comments.  Since we
don't care for or need all the RFC compliance of Email::Address,
avoiding it entirely may be preferable.

Email::Address will still be installed as a requirement for
Email::MIME, but it is only used by the
Email::MIME::header_str_set which we do not use (not even in
public-inbox).