Fix "ShouldUpdate" sample code in Mount Specs doc
Fix "ShouldUpdate" sample code in Mount Specs doc

Summary: Pull Request resolved: https://github.com/facebook/litho/pull/456

Differential Revision: D12921252

Pulled By: IanChilds

fbshipit-source-id: 9c391da9506a7cabf1e2e61fa549c276be8b7bf7

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