[Typo][Minor] typo in "A.9.3 Training with multiple GPUs"

[casinca]

Bug description

It's insignificant, just reporting for completeness, should be Distributed-Sampler instead of Distibuted-Sampler

What operating system are you using?

None

Where do you run your code?

None

Environment

[rasbt]

Thanks for the note, I appreciate it! I will pass that to the layout team.