Update 4.mdx

[rajuptvs]

updated keys to available key for the dataset.

Dataset doesn't seem to have observation.images.wrist_camera.

Updated to reflect the keys from the dataset

LeRobotDataset({
    Repository ID: 'lerobot/svla_so101_pickplace',
    Number of selected episodes: '50',
    Number of selected samples: '11939',
    Features: '['action', 'observation.state', 'observation.images.up', 'observation.images.side', 'timestamp', 'frame_index', 'episode_index', 'index', 'task_index']',
})',