munge wallet: Unify maintainer info

This makes two changes to the Portfiles for munge and wallet (which
includes subports wallet-kdc and wallet-server): I add GitHub maintainer
info, and I change my contact email address.

IIRC, these ports were created before a maintainer's GitHub account was
incuded in the Portfile's maintainer field.  So, this commit adds that
info.  At the same time, I update my contact email address to match my
current preference for contact email (as per the newer `lldpd` port).

Neither port's version or revision changes, since this change does not
affect how the port is installed.

Closes: https://trac.macports.org/ticket/72855

net/munge/Portfile

@@ -9,7 +9,7 @@ github.tarball_from tarball
 revision            2
 categories          net security
 license             {GPL-3+ LGPL-3+}
-maintainers         kornel.us:karl openmaintainer
+maintainers         {@akkornel stanford.edu:akkornel} openmaintainer
 description         Creating and validating credentials in HPC clusters.
 long_description    MUNGE (MUNGE Uid 'N' Gid Emporium) is an authentication \
                     service for creating and validating credentials.  It is \

net/wallet/Portfile

@@ -14,7 +14,7 @@ version             1.3
 revision            2
 categories          net security
 license             MIT
-maintainers         kornel.us:karl openmaintainer
+maintainers         {@akkornel stanford.edu:akkornel} openmaintainer
 description         Kerberos-authenticated secure data management
 long_description    The wallet is a system for managing secure data, \
                     authorization rules to retrieve or change that data, \