Fix deprecated yarn usage in travis.yml (#2662)
Fix deprecated yarn usage in travis.yml (#2662)

Summary:
Fixes:

> warning From Yarn 1.0 onwards, scripts don't require "--" for options to be forwarded. In a future version, any explicit "--" will be forwarded as-is to the scripts.
Pull Request resolved: https://github.com/facebook/relay/pull/2662

Reviewed By: jstejada

Differential Revision: D14210218

Pulled By: kassens

fbshipit-source-id: e90d33640015104d2b8408d6badde2a59b7d1799

kassens/relay,voideanvalue/relay,facebook/relay,atxwebs/relay,zpao/relay,wincent/relay,atxwebs/relay,kassens/relay,zpao/relay,atxwebs/relay,wincent/relay,voideanvalue/relay,josephsavona/relay,xuorig/relay,voideanvalue/relay,josephsavona/relay,facebook/relay,wincent/relay,facebook/relay,xuorig/relay,cpojer/relay,josephsavona/relay,zpao/relay,xuorig/relay,yungsters/relay,voideanvalue/relay,kassens/relay,atxwebs/relay,yungsters/relay,facebook/relay,voideanvalue/relay,iamchenxin/relay,wincent/relay,xuorig/relay,voideanvalue/relay,cpojer/relay,facebook/relay,xuorig/relay,wincent/relay,yungsters/relay,xuorig/relay,wincent/relay,iamchenxin/relay,kassens/relay,iamchenxin/relay,kassens/relay,iamchenxin/relay,kassens/relay,facebook/relay,cpojer/relay,cpojer/relay