docs: fix English FAQ title (#36222)

docs/react/faq.en-US.md

@@ -11,7 +11,7 @@ Here are the frequently asked questions about Ant Design and antd that you shoul
 
 There is currently no plan to add support for Sass/Stylus(etc.) style files, but using tools on Google you can easily convert the provided Less files to your desired style format.
 
-## Is there a difference between undefined and null in the controlled components of antd?
+## Is there a difference between `undefined` and `null` in the controlled components of `antd`?
 
 **Yes. antd will treats `undefined` as uncontrolled but `null` as controlled components which means empty value of it.**
 
@@ -21,7 +21,6 @@ But in antd, `undefined` is treated as uncontrolled, and `null` is used as an ex
 
 Note: For `options` in `Select-like` components, it is **strongly recommended not** to use `undefined` and `null` as `value` in `option`. Please use `string | number` as a valid `value` in `option`.
 
-
 ## `Select Dropdown DatePicker TimePicker Popover Popconfirm` disappears when I click another popup component inside it. How do I resolve this?
 
 This is an old bug that has been fixed since `v3.11.x`. If you're using an older version, you can use `<Select getPopupContainer={trigger => trigger.parentElement}>` to render a component inside Popover. (Or other `getXxxxContainer` props)