When the country filtering mode is enabled, it adds a "Go back" button
but the close button is right on top of it. This moves the close button
to the right to avoid any click conflicts.
To fix an annoying display bug with the top offset, an observer is used
to override the default `display: none` of the back button to keep its
flex mode but with a hidden visibility so the UI doesn't move around.
e97365f434