R1:893edf9d9558

Make Calendar Event handles slightly more modern

Summary: Ref T11326. Use modern methods instead of building this stuff separately.

Test Plan: Used `E123`, `{E123}`, saw references render normally.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T11326

Differential Revision: https://secure.phabricator.com/D16300