remove 'description' from OC_Connector_Sabre_CalDAV propertyMap

* the description field was removed in commit:
     f3f5d775b5
   but the field was still trying to be mapped - causing errors with CalDAV

apps/calendar/lib/connector_sabre.php

@@ -10,7 +10,6 @@ class OC_Connector_Sabre_CalDAV extends Sabre_CalDAV_Backend_Abstract {
 	 */
 	public $propertyMap = array(
 		'{DAV:}displayname'						  => 'displayname',
-		'{urn:ietf:params:xml:ns:caldav}calendar-description' => 'description',
 		'{urn:ietf:params:xml:ns:caldav}calendar-timezone'	=> 'timezone',
 		'{http://apple.com/ns/ical/}calendar-order'  => 'calendarorder',
 		'{http://apple.com/ns/ical/}calendar-color'  => 'calendarcolor',