[web] Use hooks instead of connect function and HOC in Calendar

Summary: Switched to hooks instead of the connect function in the Calendar class.

Test Plan: Checked if the calendar still showed up on web and worked correctly.

Reviewers: ashoat, palys-swm

Reviewed By: ashoat

Subscribers: KatPo, zrebcu411, Adrian, atul, karol-bisztyga

Differential Revision: https://phabricator.ashoat.com/D752