Remove temporary include of builtin_audio_encoder_factory.h.

Add the include to the files where it is actually used instead.

BUG=webrtc:5806

Review-Url: https://codereview.webrtc.org/2869863003
Cr-Commit-Position: refs/heads/master@{#18176}
diff --git a/webrtc/api/peerconnectioninterface.h b/webrtc/api/peerconnectioninterface.h
index a3a07b6..8c5a64b 100644
--- a/webrtc/api/peerconnectioninterface.h
+++ b/webrtc/api/peerconnectioninterface.h
@@ -74,8 +74,6 @@
 
 #include "webrtc/api/audio_codecs/audio_decoder_factory.h"
 #include "webrtc/api/audio_codecs/audio_encoder_factory.h"
-// TODO(ossu): Remove this once downstream projects have been updated.
-#include "webrtc/api/audio_codecs/builtin_audio_encoder_factory.h"
 #include "webrtc/api/datachannelinterface.h"
 #include "webrtc/api/dtmfsenderinterface.h"
 #include "webrtc/api/jsep.h"
diff --git a/webrtc/pc/peerconnectionendtoend_unittest.cc b/webrtc/pc/peerconnectionendtoend_unittest.cc
index ca9c3a3..a735ea7 100644
--- a/webrtc/pc/peerconnectionendtoend_unittest.cc
+++ b/webrtc/pc/peerconnectionendtoend_unittest.cc
@@ -11,6 +11,7 @@
 #include <memory>
 
 #include "webrtc/api/audio_codecs/builtin_audio_decoder_factory.h"
+#include "webrtc/api/audio_codecs/builtin_audio_encoder_factory.h"
 #include "webrtc/base/gunit.h"
 #include "webrtc/base/logging.h"
 #include "webrtc/base/ptr_util.h"
diff --git a/webrtc/pc/rtcstats_integrationtest.cc b/webrtc/pc/rtcstats_integrationtest.cc
index 15f0a83..03fb96c 100644
--- a/webrtc/pc/rtcstats_integrationtest.cc
+++ b/webrtc/pc/rtcstats_integrationtest.cc
@@ -12,6 +12,7 @@
 #include <vector>
 
 #include "webrtc/api/audio_codecs/builtin_audio_decoder_factory.h"
+#include "webrtc/api/audio_codecs/builtin_audio_encoder_factory.h"
 #include "webrtc/api/datachannelinterface.h"
 #include "webrtc/api/peerconnectioninterface.h"
 #include "webrtc/api/stats/rtcstats_objects.h"