update key to be persisted

configuration.nix

@@ -34,7 +34,7 @@
 
   # SOPS config
   sops = {
-    age.sshKeyPaths = [ "/etc/ssh/ssh_host_ed25519_key" ];
+    age.sshKeyPaths = [ "/persist/etc/ssh/ssh_host_ed25519_key" ];
     age.keyFile = "/var/lib/sops-nix/key.txt";
     age.generateKey = true;
     defaultSopsFormat = "json";