Reduce the amount of items in the account menu

The devices entry gone (not even Element has this) and so is the logout
action. The Switch account menu item is moved to the bottom so its
easier to access by mouse. The "Open Secret Backup" is moved under
Security settings where it lives next to the other crypto-related
settings.

src/app/qml/UnlockSSSSDialog.qml

@@ -13,7 +13,7 @@ FormCard.FormCardPage {
 
     property bool processing: false
 
-    title: i18nc("@title:window", "Load your encrypted messages")
+    title: i18nc("@title:window", "Manage Secret Backup")
 
     topPadding: Kirigami.Units.gridUnit
     leftPadding: 0