Bugfix FXIOS-9937 - Fix incorrect delete webchannel message (#21840)

The patch matches what we have in desktop and Android (see bug links),
and in addition also observes the `accountLoggedOut` message to dismiss
the `ManageFxAccountSetting` screen which would otherwise incorrectly
show the user as still signed in.

Fixes #21814

firefox-ios/Client/Frontend/Settings/SyncContentSettingsViewController.swift

@@ -9,6 +9,8 @@ import Sync
 import Account
 
 class ManageFxAccountSetting: Setting {
+    private var notification: NSObjectProtocol?
+
     let profile: Profile
 
     override var accessoryType: UITableViewCell.AccessoryType { return .disclosureIndicator }
@@ -27,6 +29,14 @@ class ManageFxAccountSetting: Setting {
                 ]
             )
         )
+
+        notification = NotificationCenter.default.addObserver(
+            forName: .accountLoggedOut,
+            object: nil,
+            queue: .main
+        ) { [weak settings] _ in
+            settings?.dismiss(animated: true, completion: nil)
+        }
     }
 
     override func onClick(_ navigationController: UINavigationController?) {
@@ -37,6 +47,12 @@ class ManageFxAccountSetting: Setting {
                                                   deepLinkParams: fxaParams)
         navigationController?.pushViewController(viewController, animated: true)
     }
+
+    deinit {
+        if let notification = notification {
+            NotificationCenter.default.removeObserver(notification)
+        }
+    }
 }
 
 class DisconnectSetting: Setting {

firefox-ios/RustFxA/FxAWebViewModel.swift

@@ -29,7 +29,7 @@ private enum RemoteCommand: String {
     case login = "fxaccounts:login"
     case changePassword = "fxaccounts:change_password"
     case signOut = "fxaccounts:logout"
-    case deleteAccount = "fxaccounts:delete_account"
+    case deleteAccount = "fxaccounts:delete"
     case profileChanged = "profile:change"
 }