rpki-client: don't leak cert in aspa_parse()

[Theo Buehler]

The cert was allocated by cert_parse_ee_cert() and needs to be freed.

Index: aspa.c
===================================================================
RCS file: /cvs/src/usr.sbin/rpki-client/aspa.c,v
retrieving revision 1.2
diff -u -p -r1.2 aspa.c
--- aspa.c      3 Sep 2022 14:40:09 -0000       1.2
+++ aspa.c      5 Sep 2022 09:10:30 -0000
@@ -251,6 +251,7 @@ aspa_parse(X509 **x509, const char *fn, 
                X509_free(*x509);
                *x509 = NULL;
        }
+       cert_free(cert);
        free(cms);
        return p.res;
 }