Remove TODO for empty samples in muxer

There is no reason to write the empty samples so keep
the behaviour same as MediaMuxer

PiperOrigin-RevId: 667495861

libraries/muxer/src/main/java/androidx/media3/muxer/Track.java

@@ -64,7 +64,6 @@ import java.util.List;
   }
 
   public void writeSampleData(ByteBuffer byteBuffer, BufferInfo bufferInfo) {
-    // TODO: b/279931840 - Confirm whether muxer should throw when writing empty samples.
     //  Skip empty samples.
     if (bufferInfo.size == 0 || byteBuffer.remaining() == 0) {
       return;