build: remove WEBRTC_CODEC_RED

gone for a while

BUG=webrtc:5922

Change-Id: Ie5d2f6dbffbc349686dbaf05a378375dbff0dce0
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/175914
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Commit-Queue: Karl Wiberg <kwiberg@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#31352}
diff --git a/modules/audio_coding/audio_coding.gni b/modules/audio_coding/audio_coding.gni
index 9b0aba8..bf67d9c 100644
--- a/modules/audio_coding/audio_coding.gni
+++ b/modules/audio_coding/audio_coding.gni
@@ -25,9 +25,6 @@
 } else {
   audio_codec_defines += [ "WEBRTC_CODEC_ISAC" ]
 }
-if (!build_with_mozilla && !build_with_chromium) {
-  audio_codec_defines += [ "WEBRTC_CODEC_RED" ]
-}
 
 audio_coding_defines = audio_codec_defines
 neteq_defines = audio_codec_defines