Update Alert English doc (ant-design#7536)

Minor edits.

components/alert/index.en-US.md

@@ -8,18 +8,18 @@ Alert component for feedback.
 
 ## When To Use
 
-- When you need to show alert messages for users.
+- When you need to show alert messages to users.
 - When you need a persistent static container which is closable by user actions.
 
 ## API
 
 | Property   | Description                                               | Type       | Default |
 |----------- |---------------------------------------------------------  | ---------- |-------|
-| type       | Type of Alert styles, options:`success`, `info`, `warning`, `error` | string | `info`, in `banner` mode it's `warning` |
+| type       | Type of Alert styles, options: `success`, `info`, `warning`, `error` | string | `info`, in `banner` mode default is `warning` |
 | closable   | Whether Alert can be closed | boolean | - |
 | closeText  | Close text to show | string\|ReactNode | - |
 | message    | Content of Alert | string\|ReactNode | - |
 | description | Additional content of Alert | string\|ReactNode | - |
-| onClose    | Callback when close Alert | Function | - |
-| showIcon   | Whether to show icon | boolean | false, in `banner` mode it's true |
+| onClose    | Callback when Alert is closed | Function | - |
+| showIcon   | Whether to show icon | boolean | false, in `banner` mode default is true |
 | banner   | Whether to show as banner | boolean | false |