Update module chrj/smtpd to v0.3.0

go.mod

 module git.autistici.org/ai3/tools/smtpd-pipe
 
-require github.com/chrj/smtpd v0.2.0
+go 1.16
+
+require github.com/chrj/smtpd v0.3.0

go.sum

 github.com/chrj/smtpd v0.2.0 h1:QGbE4UQz7sKjvXpRgNLuiBOjcWTzBKu/dj0hyDLpD14=
 github.com/chrj/smtpd v0.2.0/go.mod h1:1hmG9KbrE10JG1SmvG79Krh4F6713oUrw2+gRp1oSYk=
+github.com/chrj/smtpd v0.3.0 h1:cw1LSHDOz7N3XbkcZSF/bue9dh7ATKk5ZksfBztV6b0=
+github.com/chrj/smtpd v0.3.0/go.mod h1:1hmG9KbrE10JG1SmvG79Krh4F6713oUrw2+gRp1oSYk=
 github.com/eaigner/dkim v0.0.0-20150301120808-6fe4a7ee9cfb/go.mod h1:FSCIHbrqk7D01Mj8y/jW+NS1uoCerr+ad+IckTHTFf4=