libhydra: Remove empty unused library

testing/tests/sql/ip-split-pools-db-restart/hosts/moon/etc/strongswan.conf

@@ -9,7 +9,7 @@ charon {
   load = random nonce aes sha1 sha2 pem pkcs1 gmp x509 curl revocation hmac vici kernel-netlink socket-default updown sqlite sql attr-sql
 }
 
-libhydra {
+libstrongswan {
   plugins {
     attr-sql {
       database = sqlite:///etc/db.d/ipsec.db