maybe it is a bug, but we don’t have any widget on the left, but the template still show us 2 widgets (search and archive). Strange isn’t it. Cache cleared several times.
those are auto-placed so the Sidebar is not displayed empty. Simply add whatever widgets you require in there, and the auto-placed ones will be removed.
On the older versions of GP, those widgets are automatically displayed so the Sidebar on was never empty. On new installs of the latest version (3.0) of GP those are no longer displayed.
If you do not want any sidebar widgets then you can remove the Sidebar in Customizer > Layout > Sidebars.