Explicitly default YGNode copy ctor
Explicitly default YGNode copy ctor

Summary: No need to type out the old version. This is exactly equivalent (unless I've misread and the old version did something other than memberwise copy).

Reviewed By: davidaurelio

Differential Revision: D8842326

fbshipit-source-id: c575ea4cee6caef9ea15aaf5967597385ed26ec3

facebook/litho,facebook/litho,facebook/litho,facebook/litho,facebook/litho,facebook/litho