Update tooltip.md (#11154)

* Update tooltip.md

Add missing `'`

* Update tooltip.md

Improve textDirection text

docs/configuration/tooltip.md

@@ -42,7 +42,7 @@ Namespace: `options.plugins.tooltip`, the global options for the chart tooltips
 | `borderColor` | [`Color`](../general/colors.md) | `'rgba(0, 0, 0, 0)'` | Color of the border.
 | `borderWidth` | `number` | `0` | Size of the border.
 | `rtl` | `boolean` | | `true` for rendering the tooltip from right to left.
-| `textDirection` | `string` | canvas' default | This will force the text direction `'rtl' or 'ltr` on the canvas for rendering the tooltips, regardless of the css specified on the canvas
+| `textDirection` | `string` | canvas' default | This will force the text direction `'rtl'` or `'ltr'` on the canvas for rendering the tooltips, regardless of the css specified on the canvas
 | `xAlign` | `string` | `undefined` | Position of the tooltip caret in the X direction. [more](#tooltip-alignment)
 | `yAlign` | `string` | `undefined` | Position of the tooltip caret in the Y direction. [more](#tooltip-alignment)