Update style-props.mdx

Fix `overflowX` and `overflowY` to match the correct `overflow-*` css props

Author: jonahallibone

content/docs/styled-system/style-props.mdx

@@ -172,8 +172,8 @@ import { Box } from "@chakra-ui/react"
 | `boxSize`           | `width`, `height` | `sizes`   |
 | `verticalAlign`     | `vertical-align`  | none      |
 | `overflow`          | `overflow`        | none      |
-| `overflowX`         | `overflowX`       | none      |
-| `overflowY`         | `overflowY`       | none      |
+| `overflowX`         | `overflow-x`       | none      |
+| `overflowY`         | `overflow-y`       | none      |
 
 ### Flexbox