Fix code sample in the documentation for layouts bottomTabs (#4808)

Add curly braces around the visible property

docs/docs/layout-types.md

@@ -124,6 +124,7 @@ Navigation.mergeOptions(this.props.componentId, {
 ```
 
 ### Changing BottomTabs visibility
+
 The `visible` property can be used to control the BottomTab visibility.
 
 On **Android**, Visibility can be toggled dynamically using the `mergeOptions` command. When hiding BottomTabs, `drawBehind: true` should be specified in order for the screen to render behind the area which was previously allocated to the BottomTabs.
@@ -141,15 +142,19 @@ On **both** platforms visibility can be changed when pushing screens into a stac
 
 ```js
 Navigation.push(componentId, {
-	component: {
-	  name: 'pushedScreen',
-	  options: { bottomTabs: visible: false }
-	}
-  });
+  component: {
+    name: 'pushedScreen',
+    options: {
+      bottomTabs: {
+        visible: false
+      }
+    }
+  }
+});
 ```
 
-
 ### Updating options for a specific tab
+
 Updating (merging) tab specific options is done using the `mergeOptions` command. `mergeOptions` expects a `componentId` as first argument, therefore in order to update a specific tab we'll need to pass a `componentId` of a child of that specific tab.
 For example, Using the layout specified above, To update the `badge` property of the second tab we'll call `mergeOptions` with `SecondScreenId`.