Use SequenceChecker from public API

Bug: webrtc:12419
Change-Id: I00cca16a0ec70246156ba00b97aa7ae5ccbf5364
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/205323
Commit-Queue: Artem Titov <titovartem@webrtc.org>
Reviewed-by: Tommi <tommi@webrtc.org>
Reviewed-by: Danil Chapovalov <danilchap@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#33220}
diff --git a/rtc_base/platform_thread.h b/rtc_base/platform_thread.h
index 3438f8e..64a74d8 100644
--- a/rtc_base/platform_thread.h
+++ b/rtc_base/platform_thread.h
@@ -17,9 +17,9 @@
 #include <string>
 
 #include "absl/strings/string_view.h"
+#include "api/sequence_checker.h"
 #include "rtc_base/constructor_magic.h"
 #include "rtc_base/platform_thread_types.h"
-#include "rtc_base/synchronization/sequence_checker.h"
 
 namespace rtc {