v1.18.0

Solve lib lint failure

Summary:
This diff solves `pod lib lint` failure.

We want to make a new yoga release, as I landed some changes in its podspec which solves the broken flipper build for xcode 11.

{F221612119}

Reviewed By: passy

Differential Revision: D18382588

fbshipit-source-id: efddfa3e93ca59b79b887d04f83407b004d9a199