Avoid Element.closest() for IE 9 compatibility

Fixes #37234.

actionview/app/assets/javascripts/rails-ujs/utils/form.coffee

@@ -11,7 +11,7 @@ Rails.serializeElement = (element, additionalParam) ->
 
   inputs.forEach (input) ->
     return if !input.name || input.disabled
-    return if input.closest('fieldset[disabled]')
+    return if matches(input, 'fieldset[disabled] *')
     if matches(input, 'select')
       toArray(input.options).forEach (option) ->
         params.push(name: input.name, value: option.value) if option.selected