Fix compilation issue detected by internal tool.

webrtc/modules/audio_coding/audio_network_adaptor/fec_controller_rplr_based_unittest.cc

Index: webrtc/modules/audio_coding/audio_network_adaptor/fec_controller_rplr_based_unittest.cc
diff --git a/webrtc/modules/audio_coding/audio_network_adaptor/fec_controller_rplr_based_unittest.cc b/webrtc/modules/audio_coding/audio_network_adaptor/fec_controller_rplr_based_unittest.cc
index ce51ff00d80fc9c103b0bdebca99082ff957fc6a..f0b5d61882ea9d15d279f06e970e1ecbb67390b7 100644
--- a/webrtc/modules/audio_coding/audio_network_adaptor/fec_controller_rplr_based_unittest.cc
+++ b/webrtc/modules/audio_coding/audio_network_adaptor/fec_controller_rplr_based_unittest.cc
@@ -17,10 +17,6 @@
 
 namespace webrtc {
 
-using ::testing::NiceMock;
-using ::testing::Return;
-using ::testing::_;
-
 namespace {
 
 // The test uses the following settings: