Removing unused Opus wrapper API: WebRTCOpus_DecodePlc.

Bug: None
Change-Id: I5b613b4c13ec5f6ad13d8430043d006f6d83c11f
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/158671
Reviewed-by: Henrik Lundin <henrik.lundin@webrtc.org>
Commit-Queue: Minyue Li <minyue@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#29664}
diff --git a/modules/audio_coding/codecs/opus/opus_unittest.cc b/modules/audio_coding/codecs/opus/opus_unittest.cc
index f0f2ef0..10897fb 100644
--- a/modules/audio_coding/codecs/opus/opus_unittest.cc
+++ b/modules/audio_coding/codecs/opus/opus_unittest.cc
@@ -810,7 +810,7 @@
   // Call decoder PLC.
   int16_t* plc_buffer = new int16_t[decode_samples_per_channel * channels_];
   EXPECT_EQ(decode_samples_per_channel,
-            WebRtcOpus_DecodePlc(opus_decoder_, plc_buffer, 1));
+            WebRtcOpus_Decode(opus_decoder_, NULL, 0, plc_buffer, &audio_type));
 
   // Free memory.
   delete[] plc_buffer;