FFmpeg: Remove unnecessary metadata update signal

This signal was leading to track change notification popups when the
track started buffering, way ahead of when the change was actually
auduble. Callers will already be retrieving metadata at this point
regardless of the notification.

Signed-off-by: Christopher Snowhill <kode54@gmail.com>

Author: kode54

Plugins/FFMPEG/FFMPEGDecoder.m

@@ -564,11 +564,6 @@ - (BOOL)open:(id<CogSource>)s {
 		prebufferedChunk = [self readAudio];
 	}
 
-	if(metadataUpdated) {
-		[self willChangeValueForKey:@"metadata"];
-		[self didChangeValueForKey:@"metadata"];
-	}
-
 	return YES;
 }