EmailBundle:Form/Model/Email::removeAttachment - collection::remove expects a key as arg, not value (attachment)

vendor/oro/platform/src/Oro/Bundle/EmailBundle/Form/Model/Email.php

```
public function removeAttachment(EmailAttachment $attachment)
{
    if ($this->attachments->contains($attachment)) {
        $this->attachments->remove($attachment);
    }
}
```

remove() expect a collection key but a collection value is provide in current code.