Delete old video defines in engine config.

This CL deletes the old and not used video defines in
engine_configurations.h and pre-pends voice_ to indicate there are only
voice/audio defines left in the file.

BUG=none
R=solenberg@webrtc.org

Review URL: https://codereview.webrtc.org/2401673002 .

Cr-Commit-Position: refs/heads/master@{#14558}
diff --git a/webrtc/modules/audio_coding/acm2/codec_manager.cc b/webrtc/modules/audio_coding/acm2/codec_manager.cc
index f028c45..d8dcd79 100644
--- a/webrtc/modules/audio_coding/acm2/codec_manager.cc
+++ b/webrtc/modules/audio_coding/acm2/codec_manager.cc
@@ -12,9 +12,9 @@
 
 #include "webrtc/base/checks.h"
 #include "webrtc/base/format_macros.h"
-#include "webrtc/engine_configurations.h"
 #include "webrtc/modules/audio_coding/acm2/rent_a_codec.h"
 #include "webrtc/system_wrappers/include/trace.h"
+#include "webrtc/voice_engine_configurations.h"
 
 namespace webrtc {
 namespace acm2 {