Bug 700714 - Remove `delete_selected` action from the admin.

There is one more way to do this:

```py
def get_actions(self, request):
    actions = super(ProfileAdmin, self).get_actions(request)
    if 'delete_selected' in actions:
        del actions['delete_selected']
    return actions
```

https://bugzilla.mozilla.org/show_bug.cgi?id=700714