Docs: Remove link to nonexistent RelayValidator (#2980)
Docs: Remove link to nonexistent RelayValidator (#2980)

Summary:
Link doesn't work, `RelayValidator` was removed here: https://github.com/facebook/relay/commit/15e8d2201fdad47596e1acfb3a5daa3fb7511a8e
Pull Request resolved: https://github.com/facebook/relay/pull/2980

Differential Revision: D19260765

Pulled By: kassens

fbshipit-source-id: 3712493e293b0e77f4788afaeb868a8d23d93bee

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