Cleanup expired field trial WebRTC-Avx2SupportKillSwitch

Bug: webrtc:42221774
Change-Id: I92fab7d14fd0c2a9fd10e91fbad9c2831d7415ac
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/349643
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Commit-Queue: Danil Chapovalov <danilchap@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#42233}
diff --git a/experiments/field_trials.py b/experiments/field_trials.py
index f69a6eb..73d6437 100755
--- a/experiments/field_trials.py
+++ b/experiments/field_trials.py
@@ -484,9 +484,6 @@
     FieldTrial('WebRTC-AutomaticAnimationDetectionScreenshare',
                42221141,
                date(2024, 4, 1)),
-    FieldTrial('WebRTC-Avx2SupportKillSwitch',
-               42221774,
-               date(2024, 4, 1)),
     FieldTrial('WebRTC-BindUsingInterfaceName',
                42220770,
                date(2024, 4, 1)),
@@ -884,7 +881,7 @@
 ])  # yapf: disable
 
 POLICY_EXEMPT_FIELD_TRIALS_DIGEST: str = \
-    'a84804e20ae8a5f63996e59560ca97d724665c20'
+    '84f7bc41874cd36cc4d5306e86972f53fef83f29'
 
 REGISTERED_FIELD_TRIALS: FrozenSet[FieldTrial] = ACTIVE_FIELD_TRIALS.union(
     POLICY_EXEMPT_FIELD_TRIALS)
diff --git a/system_wrappers/BUILD.gn b/system_wrappers/BUILD.gn
index 2576d4e..6fd7f48 100644
--- a/system_wrappers/BUILD.gn
+++ b/system_wrappers/BUILD.gn
@@ -31,7 +31,6 @@
   defines = []
   libs = []
   deps = [
-    ":field_trial",
     "../api:array_view",
     "../api/units:timestamp",
     "../modules:module_api_public",
diff --git a/system_wrappers/source/cpu_features.cc b/system_wrappers/source/cpu_features.cc
index 8cd701e..4a6170c 100644
--- a/system_wrappers/source/cpu_features.cc
+++ b/system_wrappers/source/cpu_features.cc
@@ -12,7 +12,6 @@
 
 #include "rtc_base/system/arch.h"
 #include "system_wrappers/include/cpu_features_wrapper.h"
-#include "system_wrappers/include/field_trial.h"
 
 #if defined(WEBRTC_ARCH_X86_FAMILY) && defined(_MSC_VER)
 #include <intrin.h>
@@ -78,8 +77,7 @@
     return 0 != (cpu_info[2] & 0x00000001);
   }
 #if defined(WEBRTC_ENABLE_AVX2)
-  if (feature == kAVX2 &&
-      !webrtc::field_trial::IsEnabled("WebRTC-Avx2SupportKillSwitch")) {
+  if (feature == kAVX2) {
     int cpu_info7[4];
     __cpuid(cpu_info7, 0);
     int num_ids = cpu_info7[0];