Fix schema, maintainers are usually an array

pkgs/applications/networking/droopy/default.nix

···
     description = "Mini Web server that let others upload files to your computer";
     homepage = http://stackp.online.fr/droopy;
     license = licenses.bsd3;
-    maintainers = maintainers.profpatsch;
+    maintainers = [ maintainers.profpatsch ];
   };
 
 }