Double padding around cookie message close button.

Button was right up against the edge and being interfered with by scroll bars.  We now also have larger tap area.

I've uploaded a few screengrabs on [the target process ticket](https://moneyadviceservice.tpondemand.com/Project/Planning/Kanban/KanbanBoard.aspx?acid=E10E3BF21A3627FAEC297AE412030D57) to see the change.