[11.x] Remove useless variable assignment

[seriquynh]

The $request variable inside Illuminate\Http\Resources\Json\JsonResource::resolve() is useless, so I remove it.

public function resolve($request = null)
{
    $data = $this->toArray(
        // It's unneeded to re-assign $request here.
        $request = $request ?: Container::getInstance()->make('request')
    );

    if ($data instanceof Arrayable) {
        $data = $data->toArray();
    } elseif ($data instanceof JsonSerializable) {
        $data = $data->jsonSerialize();
    }

    return $this->filter((array) $data);
}