Update thread annotiation macros in rtc_base to use RTC_ prefix

webrtc/rtc_base/rate_limiter.h

Index: webrtc/rtc_base/rate_limiter.h
diff --git a/webrtc/rtc_base/rate_limiter.h b/webrtc/rtc_base/rate_limiter.h
index b4b9080faa807323f4e8bec9b384f231218f7e7a..e3f6249a5eea309f6d28f87fdfb438f543928f99 100644
--- a/webrtc/rtc_base/rate_limiter.h
+++ b/webrtc/rtc_base/rate_limiter.h
@@ -44,9 +44,9 @@ class RateLimiter {
  private:
   const Clock* const clock_;
   rtc::CriticalSection lock_;
-  RateStatistics current_rate_ GUARDED_BY(lock_);
-  int64_t window_size_ms_ GUARDED_BY(lock_);
-  uint32_t max_rate_bps_ GUARDED_BY(lock_);
+  RateStatistics current_rate_ RTC_GUARDED_BY(lock_);
+  int64_t window_size_ms_ RTC_GUARDED_BY(lock_);
+  uint32_t max_rate_bps_ RTC_GUARDED_BY(lock_);
 
   RTC_DISALLOW_IMPLICIT_CONSTRUCTORS(RateLimiter);
 };