[Doc] replace s002 with seq002 in README.md

[yuji38kwmt]

In README.md, variable s002 is used but s002 does not defined.

>>> pc0 = s002.lidar[0]
>>> print(pc0.shape)
(166768, 6)
>>> s002.lidar.set_sensor(0)  # set to include only mechanical 360° LiDAR
>>> pc0_sensor0 = s002.lidar[0]
>>> print(pc0_sensor0.shape)
(106169, 6)
>>> s002.lidar.set_sensor(1)  # set to include only front-facing LiDAR
>>> pc0_sensor1 = s002.lidar[0]
>>> print(pc0_sensor1.shape)
(60599, 6)

So I replaced s002 with seq002 in README.md