Update material-top-tab-navigator.md (react-navigation#1033)

Author: adamsythe

versioned_docs/version-6.x/material-top-tab-navigator.md

@@ -100,7 +100,7 @@ String indicating whether the keyboard gets dismissed in response to a drag gest
 Object containing the initial height and width of the screens. Passing this will improve the initial rendering performance. For most apps, this is a good default:
 
 ```js
-{ width: Dimensions.get('window').width }}
+{ width: Dimensions.get('window').width }
 ```
 
 #### `sceneContainerStyle`