deskutils/calcurse: Remove expired py-oauth2client dependency

Removes the 'security/py-oauth2client' dependency. This fixes the
DEPRECATED status.

CalDAV now supports only basic authentication. OAuth2-based services
(like Google Calendar) will no longer function.

MFH: 2025Q2
(cherry picked from commit a6af0e6bbb6d3bce15671b100fa58e82703e4c37)