Revert "endSessionDialog: apply updates by default"

Turns out it's not that clear in which cases we want to apply updates
and in which ones we shouldn't. For example one case is when the device
is running on battery, where we currently display a warning, but still
install updates by default.

So let's revert that again for now and hopefully work out a proper
concept for updates in the future.

This reverts commit ddb85c03c3.

https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/1228

js/ui/endSessionDialog.js

@@ -680,7 +680,7 @@ class EndSessionDialog extends ModalDialog.ModalDialog {
 
         _setCheckBoxLabel(this._checkBox, dialogContent.checkBoxText || '');
         this._checkBox.visible = dialogContent.checkBoxText && updatePrepared && updatesAllowed;
-        this._checkBox.checked = this._checkBox.visible;
+        this._checkBox.checked = updatePrepared && updateTriggered;
 
         // We show the warning either together with the checkbox, or when
         // updates have already been triggered, but the user doesn't have