undef DEAD_CERT_LIFETIME too in trusted_dirs_remove_old_certs()

In trusted_dirs_remove_old_certs() we have

#define DEAD_CERT_LIFETIME (2*24*60*60)
#define OLD_CERT_LIFETIME (7*24*60*60)
[...use them...]
#undef OLD_CERT_LIFETIME

Shouldn't we undef both (or neither)?

Introduced in git commit 8157b8b7.