Fix changelog formatting
Fix changelog formatting

Summary: Fix date formatting in Changelog

Reviewed By: muraziz

Differential Revision: D24361099

fbshipit-source-id: 8ad102f1f4750d89079a83d4179a5b1f3fecec91

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