Replace expired OpenPGP certficates
With a version of GnuPG in debian that defends against a signature verification denial of service, the test suite in Mail::GnuPG breaks on its signatures that come from expired certificates.
See https://dev.gnupg.org/T7547 for more details.
This patch repairs the test suite for either variant of GnuPG.
This addresses https://bugs.debian.org/1099112