fix importers/calendar_event_spec

Change-Id: Ie64bf50f780d20ca0e09e0aeb8d709fc6d9f2859
Reviewed-on: https://gerrit.instructure.com/33716
Reviewed-by: Brian Palmer <brianp@instructure.com>
Product-Review: Brian Palmer <brianp@instructure.com>
QA-Review: Brian Palmer <brianp@instructure.com>
Tested-by: Brian Palmer <brianp@instructure.com>