HDR: Add comment to clarify lack of support HDR10 for AVC

PiperOrigin-RevId: 465360186
(cherry picked from commit 34866228)

libraries/transformer/src/main/java/androidx/media3/transformer/EncoderUtil.java

@@ -125,6 +125,7 @@ public final class EncoderUtil {
         if (colorTransfer == C.COLOR_TRANSFER_HLG) {
         if (colorTransfer == C.COLOR_TRANSFER_HLG) {
           return ImmutableList.of(MediaCodecInfo.CodecProfileLevel.AVCProfileHigh10);
           return ImmutableList.of(MediaCodecInfo.CodecProfileLevel.AVCProfileHigh10);
         }
         }
+        // CodecProfileLevel does not support PQ/HDR10 for H264.
         break;
         break;
       case MimeTypes.VIDEO_H265:
       case MimeTypes.VIDEO_H265:
         if (colorTransfer == C.COLOR_TRANSFER_HLG) {
         if (colorTransfer == C.COLOR_TRANSFER_HLG) {