perlPackages.MailDKIM: add missing CryptX dependency (NixOS#366744)

We've been getting `Can't locate Crypt/PK/Ed25519.pm in @INC` when
trying to `use Mail::DKIM::PrivateKey`. This is especially critical as
this crashed our sympa instance.

pkgs/top-level/perl-packages.nix

@@ -15048,7 +15048,7 @@ with self; {
       url = "mirror://cpan/authors/id/M/MB/MBRADSHAW/Mail-DKIM-1.20230911.tar.gz";
       hash = "sha256-kecxcoK3JM+9LJtuZjDvFDKISLb8UgPv1w3sL7hyaMo=";
     };
-    propagatedBuildInputs = [ CryptOpenSSLRSA MailAuthenticationResults MailTools NetDNS ];
+    propagatedBuildInputs = [ CryptOpenSSLRSA CryptX MailAuthenticationResults MailTools NetDNS ];
     doCheck = false; # tries to access the domain name system
     buildInputs = [ NetDNSResolverMock TestRequiresInternet YAMLLibYAML ];
     meta = {