remove redundant (duplicate) code example (#1234)

Author: sashsvamir

src/guide/component-custom-events.md

@@ -89,9 +89,6 @@ app.component('my-component', {
 })
 ```
 
-```html
-<my-component v-model:title="bookTitle"></my-component>
-```
 
 ## Multiple `v-model` bindings