Clarify comment for coro::merge()
Clarify comment for coro::merge()

Summary: Based on scsiguy's feedback. Probably it can be made shorter and clearer still, feel free to propose more changes.

Reviewed By: scsiguy

Differential Revision: D33591287

fbshipit-source-id: e0bf85ebfd98d7032ddbd54c69c52b33525a62c7

facebook/folly,facebook/folly,facebook/folly,facebook/folly,facebook/folly