Remove the #enable-fast-user-switcher flag.

chrome/app/generated_resources.grd

Index: chrome/app/generated_resources.grd
diff --git a/chrome/app/generated_resources.grd b/chrome/app/generated_resources.grd
index 84f4c3da89be3120a61f2e5f91f370eb9b55732c..ebbdece42c61b7c318eb1ee8a1745f4a9bfaeec2 100644
--- a/chrome/app/generated_resources.grd
+++ b/chrome/app/generated_resources.grd
@@ -14348,12 +14348,6 @@ After you create a new supervised user, you can manage their settings at any tim
       <message name="IDS_FLAGS_ENABLE_ACCOUNT_CONSISTENCY_DESCRIPTION" desc="Description for the flag to enable the account consistency between browser and cookie jar.">
         When enabled, the browser manages signing in and out of Google accounts.
       </message>
-      <message name="IDS_FLAGS_ENABLE_FAST_USER_SWITCHING_NAME" desc="Title for the flag to enable fast user switching.">
-        Enable fast user switching in the avatar menu
-      </message>
-      <message name="IDS_FLAGS_ENABLE_FAST_USER_SWITCHING_DESCRIPTION" desc="Description for the flag to enable fast user switching">
-        Enables fast switching between users in the avatar menu.
-      </message>
       <message name="IDS_FLAGS_ENABLE_NEW_AVATAR_MENU_NAME" desc="Title for the flag to enable the new avatar menu.">
         Enable the new avatar menu
       </message>