Remove unused mention of InitFieldTrialsFromString in media unittests

Bug: webrtc:42225026
Change-Id: I7f63d9c23145287022342f9ef3345856633dd013
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/392981
Auto-Submit: Danil Chapovalov <danilchap@webrtc.org>
Reviewed-by: Per Kjellander <perkj@webrtc.org>
Commit-Queue: Danil Chapovalov <danilchap@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#44720}
diff --git a/media/BUILD.gn b/media/BUILD.gn
index a11de12..4778231 100644
--- a/media/BUILD.gn
+++ b/media/BUILD.gn
@@ -1039,7 +1039,6 @@
         "../rtc_base/experiments:min_video_bitrate_experiment",
         "../rtc_base/system:file_wrapper",
         "../system_wrappers",
-        "../system_wrappers:field_trial",
         "../test:audio_codec_mocks",
         "../test:fake_video_codecs",
         "../test:field_trial",
diff --git a/media/engine/internal_decoder_factory_unittest.cc b/media/engine/internal_decoder_factory_unittest.cc
index 17c3b13..d5a30c1 100644
--- a/media/engine/internal_decoder_factory_unittest.cc
+++ b/media/engine/internal_decoder_factory_unittest.cc
@@ -18,7 +18,6 @@
 #include "api/video_codecs/video_decoder.h"
 #include "api/video_codecs/video_decoder_factory.h"
 #include "media/base/media_constants.h"
-#include "system_wrappers/include/field_trial.h"
 #include "test/gmock.h"
 #include "test/gtest.h"
 
@@ -28,8 +27,6 @@
 using ::testing::Field;
 using ::testing::Not;
 
-using field_trial::InitFieldTrialsFromString;
-
 #ifdef RTC_ENABLE_VP9
 constexpr bool kVp9Enabled = true;
 #else