libhydra: Remove empty unused library

testing/tests/ikev2/ip-pool-db/hosts/moon/etc/strongswan.conf

@@ -4,7 +4,7 @@ charon {
   load = aes des sha1 sha2 md5 pem pkcs1 gmp random nonce x509 curl revocation hmac xcbc stroke kernel-netlink socket-default sqlite attr-sql updown
 }
 
-libhydra {
+libstrongswan {
   plugins {
     attr-sql {
       database = sqlite:///etc/db.d/ipsec.db