BUG Default form submits to text/html, fixing validation (#7653)

Was using text/json, which Form->httpSubmission() interprets
(correctly) to returning JSON validation data.
This trips up the interface, which expects HTML with
the validation errors directly in the markup.

admin/javascript/LeftAndMain.js

@@ -253,8 +253,7 @@ jQuery.noConflict();
 						});
 
 						newForm.trigger('aftersubmitform', {status: status, xhr: xhr, formData: formData});
-					}, 
-					dataType: 'json'
+					}
 				}, ajaxOptions));
 
 				return false;