Update Popover English doc (#7633)

Fixed typos.

components/popover/index.en-US.md

@@ -16,11 +16,11 @@ Comparing with `Tooltip`, besides information `Popover` card can also provide ac
 
 | Param     | Description   | Type     | Default value       |
 |-----------|------------------------------------------|---------------|--------|
-| title     | title of the card                                 | string\|ReactNode | none     |
-| content   | content of the card                            | string\|ReactNode | none     |
+| title     | Title of the card                                 | string\|ReactNode | - |
+| content   | Content of the card                            | string\|ReactNode | - |
 
 Consult [Tooltip's documentation](https://ant.design/components/tooltip/#API) to find more APIs.
 
 ## Note
 
-Please ensure that the child node of `Popover` accepts `onMouseEnter`, `onMouseLeave`, `onFocus`, `onClick` event.
+Please ensure that the child node of `Popover` accepts `onMouseEnter`, `onMouseLeave`, `onFocus`, `onClick` events.