R1:8ce8a761efe9

Remove PHUICalendarWidgetView

Summary: This class is unused after D11547.

Test Plan: `grep`

Reviewers: chad, epriestley, #blessed_reviewers

Reviewed By: epriestley, #blessed_reviewers

Subscribers: Korvin, epriestley

Differential Revision: https://secure.phabricator.com/D12569