Don't catch other 4xx errors

app/webpacker/js/turbo.js

@@ -20,11 +20,12 @@ document.addEventListener("turbo:submit-end", (event) => {
 });
 
 function showError(status) {
+  // Note that other 4xx errors will be handled differently.
   if(status == 401) {
     alert(I18n.t("errors.unauthorized.message"));
   } else if(status === undefined) {
     alert(I18n.t("errors.network_error.message"));
-  } else {
+  } else if (status >= 500) {
     alert(I18n.t("errors.general_error.message"));
   }
 }