Remove the iOS QR Code scanner experiment code.

ios/chrome/browser/about_flags.mm

Index: ios/chrome/browser/about_flags.mm
diff --git a/ios/chrome/browser/about_flags.mm b/ios/chrome/browser/about_flags.mm
index a681f344ee0adb8c3a9eba782d285989ca2a0cf3..b93b9d44ed634dc5d835ad51cd7163e80523fbc9 100644
--- a/ios/chrome/browser/about_flags.mm
+++ b/ios/chrome/browser/about_flags.mm
@@ -227,13 +227,6 @@ void AppendSwitchesFromExperimentalSettings(base::CommandLine* command_line) {
                                     web::BuildUserAgentFromProduct(product));
   }
 
-  // Populate command line flags from QRScanner.
-  if ([defaults boolForKey:@"DisableQRCodeReader"]) {
-    command_line->AppendSwitch(switches::kDisableQRScanner);
-  } else {
-    command_line->AppendSwitch(switches::kEnableQRScanner);
-  }
-
   // Populate command line flag for the Payment Request API.
   NSString* enable_payment_request =
       [defaults stringForKey:@"EnablePaymentRequest"];