Merge pull request #45053 from nextcloud/backport/44938/stable29

[stable29] fix(CalDAV): remove UNKNOWN from room / resource consideration

apps/dav/lib/CalDAV/Schedule/IMipService.php

@@ -682,7 +682,7 @@ public function isRoomOrResource(Property $attendee): bool {
 			return false;
 		}
 		$type = $cuType->getValue() ?? 'INDIVIDUAL';
-		if (\in_array(strtoupper($type), ['RESOURCE', 'ROOM', 'UNKNOWN'], true)) {
+		if (\in_array(strtoupper($type), ['RESOURCE', 'ROOM'], true)) {
 			// Don't send emails to things
 			return true;
 		}