[docs] the comment of concat_samples() methods may have mistakes？

[colourfulspring]

Description

Hello,

I found you have provided a testcode to show how to use the concat_samples function. However, in the testcode, you defined 2 variables c1 and c2 at Line 1564-1569, but after that, you run print(concat_samples([b1, b2])) at Line 1570. Finally, you said the testoutput is an instance of MultiAgentBatch at Line 1575-1576.

In my opinion, maybe here is a simple typing mistake. print(concat_samples([b1, b2])) at Line 1570 should be print(concat_samples([c1, c2])). Hope you can reply.

Link

https://github.com/ray-project/ray/blob/master/rllib/policy/sample_batch.py#L1570