R1:f44a9a4e4896

Remove "isCancelledEvent()" wrapper on Calendar Events

Summary: Ref T11804. The field now reads the correct value directly and we don't need this wrapper.

Test Plan: Poked around Calendar without explosions.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T11804

Differential Revision: https://secure.phabricator.com/D16779