Opus wrapper: remove misleading comment

- WebRTC does use the libopus DTX implementation
- The removed detail is anyways irrelevant in a docstring

Bug: webrtc:376493209
Change-Id: I3dfe1521259e596dbfa0db97f91ffb75deeb16b8
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/367200
Commit-Queue: Alessio Bazzica <alessiob@webrtc.org>
Reviewed-by: Jakob Ivarsson‎ <jakobi@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#43344}
diff --git a/modules/audio_coding/codecs/opus/opus_interface.h b/modules/audio_coding/codecs/opus/opus_interface.h
index 733f7e4..dd64e82 100644
--- a/modules/audio_coding/codecs/opus/opus_interface.h
+++ b/modules/audio_coding/codecs/opus/opus_interface.h
@@ -421,9 +421,7 @@
  *
  * Output:
  *      - decoded            : The decoded vector
- *      - audio_type         : 1 normal, 2 CNG (for Opus it should
- *                             always return 1 since we're not using Opus's
- *                             built-in DTX/CNG scheme)
+ *      - audio_type         : 1 normal, 2 CNG
  *
  * Return value              : >0 - Samples per channel in decoded vector
  *                             -1 - Error