Fix replaced nixseparatedebuginfod

nixseparatedebuginfod has been replaced by nixseparatedebuginfod2

Reviewed-by: Rodrigo Arias Mallo <rodrigo.arias@bsc.es>

m/module/debuginfod.nix

@@ -1,3 +1,10 @@
 {
-  services.nixseparatedebuginfod.enable = true;
+  services.nixseparatedebuginfod2 = {
+    enable = true;
+    substituters = [
+      "local:"
+      "https://cache.nixos.org"
+      "http://hut/cache"
+    ];
+  };
 }