fix(BackupSeedModal): always show vertical scrollbar

This is to ensure users don't get confused with the fact there's
more checkboxes to check in the modal until they can continue.

Depending on viewport size, checkboxes can be hidden but it's not
obvious that the area is scrollable.

See #8651

Closes #8651

ui/app/AppLayouts/Profile/popups/backupseed/Acknowledgements.qml

@@ -1,4 +1,5 @@
 import QtQuick 2.12
+import QtQuick.Controls 2.14
 import QtQuick.Layouts 1.12
 
 import shared.panels 1.0
@@ -33,6 +34,8 @@ ColumnLayout {
                 anchors.margins: -parent.anchors.margins
                 anchors.bottomMargin: -parent.anchors.bottomMargin
 
+                ScrollBar.vertical.policy: ScrollBar.AlwaysOn
+
                 clip: false
 
                 ColumnLayout {