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}

modules/audio_coding/test/TestRedFec.h

@@ -14,13 +14,12 @@
 #include <memory>
 #include <string>
 
-#include "modules/audio_coding/test/ACMTest.h"
 #include "modules/audio_coding/test/Channel.h"
 #include "modules/audio_coding/test/PCMFile.h"
 
 namespace webrtc {
 
-class TestRedFec : public ACMTest {
+class TestRedFec {
  public:
   explicit TestRedFec();
   ~TestRedFec();