Delete support for enabling adaptive isac mode

This appears unused. If deleted, other code related to isac bandwidth
estimation becomes unused and may be deleted in followup cls.

Bug: webrtc:10098
Change-Id: Ifeac2e90de895b12c337ea28cc33704350b9abf4
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/153667
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Commit-Queue: Niels Moller <nisse@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#29252}
diff --git a/modules/audio_coding/BUILD.gn b/modules/audio_coding/BUILD.gn
index 8c5fb00..43b1d9b 100644
--- a/modules/audio_coding/BUILD.gn
+++ b/modules/audio_coding/BUILD.gn
@@ -370,15 +370,13 @@
   ]
 }
 
-rtc_static_library("isac_common") {
+rtc_source_set("isac_common") {
   poisonous = [ "audio_codecs" ]
   sources = [
     "codecs/isac/audio_decoder_isac_t.h",
     "codecs/isac/audio_decoder_isac_t_impl.h",
     "codecs/isac/audio_encoder_isac_t.h",
     "codecs/isac/audio_encoder_isac_t_impl.h",
-    "codecs/isac/locked_bandwidth_info.cc",
-    "codecs/isac/locked_bandwidth_info.h",
   ]
   deps = [
     ":isac_bwinfo",