Remove unecessary prepend

I was wondering why do you need to add one space inside the `<p>` while disabling the selection ?

Because, first I fixed multiple spaces addition (when use click a lot inside the embed placeholder) using this snippet:

```javascript
// do not add multiple spaces, one is enough
if (0 !== $place.html().indexOf('&nbsp;')) {
    $place.prepend('&nbsp;');
}
```

And then I removed the `prepend` and everything still works... :)