Remove the useless ACMTest base class

Bug: webrtc:8396
Change-Id: I021a2429910b21ffe4829e0ed51b9290bc715c0c
Reviewed-on: https://webrtc-review.googlesource.com/102884
Reviewed-by: Niels Moller <nisse@webrtc.org>
Commit-Queue: Karl Wiberg <kwiberg@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#24907}
diff --git a/modules/audio_coding/test/opus_test.h b/modules/audio_coding/test/opus_test.h
index 1356f27..019e96b 100644
--- a/modules/audio_coding/test/opus_test.h
+++ b/modules/audio_coding/test/opus_test.h
@@ -17,14 +17,13 @@
 
 #include "modules/audio_coding/acm2/acm_resampler.h"
 #include "modules/audio_coding/codecs/opus/opus_interface.h"
-#include "modules/audio_coding/test/ACMTest.h"
 #include "modules/audio_coding/test/Channel.h"
 #include "modules/audio_coding/test/PCMFile.h"
 #include "modules/audio_coding/test/TestStereo.h"
 
 namespace webrtc {
 
-class OpusTest : public ACMTest {
+class OpusTest {
  public:
   OpusTest();
   ~OpusTest();