[media.ccc.de] Recent kiosk: Add comment clarifying "length" and "duration" fields have the same value

extractor/src/main/java/org/schabi/newpipe/extractor/services/media_ccc/extractors/MediaCCCRecentKioskExtractor.java

@@ -46,6 +46,8 @@ public class MediaCCCRecentKioskExtractor implements StreamInfoItemExtractor {
 
     @Override
     public long getDuration() throws ParsingException {
+        // duration and length have the same value
+        // see https://github.com/voc/voctoweb/blob/master/app/views/public/shared/_event.json.jbuilder
         return event.getInt("duration");
     }