remove incorrect prototype

panda/src/express/config_express.cxx

@@ -38,8 +38,6 @@ ConfigureDef(config_express);
 NotifyCategoryDef(express, "");
 NotifyCategoryDef(thread, "");
 
-extern void init_system_type_handles();
-
 ConfigureFn(config_express) {
   init_libexpress();
 }