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

components/signin/core/common/signin_switches.cc

Index: components/signin/core/common/signin_switches.cc
diff --git a/components/signin/core/common/signin_switches.cc b/components/signin/core/common/signin_switches.cc
index a86458fe66518c9915b3ee0860288e64cd1122c0..2e1950ca103f2724286332083138aa40f9dc649b 100644
--- a/components/signin/core/common/signin_switches.cc
+++ b/components/signin/core/common/signin_switches.cc
@@ -42,10 +42,6 @@ extern const char kEnableRefreshTokenAnnotationRequest[] =
 // Enables multiple account versions of chrome.identity APIs.
 const char kExtensionsMultiAccount[] = "extensions-multi-account";
 
-// Allows displaying the list of existing profiles in the avatar bubble for
-// fast switching between profiles.
-const char kFastUserSwitching[] = "fast-user-switching";
-
 // Enables using GAIA information to populate profile name and icon.
 const char kGoogleProfileInfo[] = "google-profile-info";