Remove toast property from flash data object

[realihorrud]

Hi there,

This PR involves removing a toast property from flash object, because as it seemed for me, earlier in examples we only have:

Inertia::flash([
        'message' => 'User created!',
        'newUserId' => $user->id,
    ]);

and not:

Inertia::flash([
        'toast' => ['message' => 'User created!', ...]
    ]);

Hope it does make sense, at least I've spent quite a few dozen of minutes figuring out, that there is no toast property on flash object, but only what I had already specified. Maybe I'm wrong and you can correct me, but in reality there's no toast on flash by default as I thought.

Thanks.