[fanny] set persistentKeepalive

to be able to ssh even if fanny was not active for a while

machines/modules/malobeo/peers.nix

@@ -34,5 +34,6 @@
     address = [ "10.100.0.101/24" ];
     allowedIPs = [ "10.100.0.101/32" ];
     publicKey = "3U59F6T1s/1LaZBIa6wB0qsVuO6pRR9jfYZJIH2piAU=";
+    persistentKeepalive = 25;
   };
 }