Remove autoplay-muted-videos feature flag.

content/public/common/content_features.cc

Index: content/public/common/content_features.cc
diff --git a/content/public/common/content_features.cc b/content/public/common/content_features.cc
index 656b8fb78f25e535e8a6834d33a8675d84a6471b..ea2be83f8c448591e5c05be913ee5b73176595af 100644
--- a/content/public/common/content_features.cc
+++ b/content/public/common/content_features.cc
@@ -239,10 +239,6 @@ const base::Feature kSendBeaconThrowForBlobWithNonSimpleType{
     base::FEATURE_DISABLED_BY_DEFAULT};
 
 #if defined(OS_ANDROID)
-// Allow videos to autoplay without a user gesture if muted.
-const base::Feature kAutoplayMutedVideos{"AutoplayMutedVideos",
-                                         base::FEATURE_ENABLED_BY_DEFAULT};
-
 // Use IME's own thread instead of using main UI thread. It also means that
 // we will not use replica editor and do a round trip to renderer to synchronize
 // with Blink data.