fix(caldav): Fix wrong Psalm report for nullable calendar data

> Docblock-defined type Sabre\VObject\Component\VCalendar for $vcalendar is never falsy

^ is a lie

Signed-off-by: Christoph Wurst <christoph@winzerhof-wurst.at>

apps/dav/lib/CalDAV/Reminder/ReminderService.php

@@ -217,7 +217,6 @@ class ReminderService {
 			return;
 		}
 
-		/** @var VObject\Component\VCalendar $vcalendar */
 		$vcalendar = $this->parseCalendarData($calendarData);
 		if (!$vcalendar) {
 			return;