fix: normals plot titles copy-pasted from instance id

[andrewwhitecdw]

This PR addresses the following issue in examples/02_draw_images.py: normals plot titles copy-pasted from instance id.

Changes

• examples/02_draw_images.py: normals plot titles copy-pasted from instance id.

Details

Before:

    plt.title('left instance id')
    plt.imshow(images['robot.front_camera.left.normals_image'])
    plt.subplot(nrows, 2, 8)
    plt.title('right instance id')
    plt.imshow(images['robot.front_camera.right.normals_image'])

After:

    plt.title('left normals')
    plt.imshow(images['robot.front_camera.left.normals_image'])
    plt.subplot(nrows, 2, 8)
    plt.title('right normals')
    plt.imshow(images['robot.front_camera.right.normals_image'])