Fix formatting in PortForwarding readme
Fix formatting in PortForwarding readme

Summary: Pull Request resolved: https://github.com/facebook/flipper/pull/369

Differential Revision: D14031906

Pulled By: passy

fbshipit-source-id: 6da0ab7da30f7505b5265033f732a00cf9f397a4

facebook/flipper,facebook/flipper,facebook/flipper,facebook/flipper,facebook/flipper,facebook/flipper,facebook/flipper,facebook/flipper,facebook/flipper,facebook/flipper,facebook/flipper