Remove unnecessary atomic from folly::coro::collectAny
Remove unnecessary atomic from folly::coro::collectAny

Summary: The CancellationSource already provides this synchronization

Reviewed By: yfeldblum

Differential Revision: D29368728

fbshipit-source-id: 085467d1fcb70d6fc059174ec673f7825025c076

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