security/pam_krb5: Revert "security/pam_krb5: IGNORE for CVE-2023-3326"

Discussing with our upstream, he is aware of CVE-2023-3326. Work to
add generalized anti-spoofing is planned. In the mean time he
recommends using FAST (anon_fast) to mitigate CVE-2023-3326. anon_fast
already includes built-in anti-spoofing.

More discussion is here:
https://github.com/rra/pam-krb5/blob/main/docs/pam_krb5.pod#L53

This reverts commit 41afd03d9c8e76fe42c555b1274fec069f83ecae.