Fix keyboard navigation on search pages

Some of our search pages (such as the room and user search) has a list header item. Due to how this works, it's not actually a part of the list view keyboard navigation and a whole separate item. So in the tab order, it comes after the list view which makes no sense. And it's part of the list view, so users must expect it to be selectable with the up and down arrows like other items.

This simple change makes it so it behaves as expected. The first actual list item is selected by default, but it's possible to navigate to the list header item via the up arrow key and then return to the list view using the down arrow. The list header item is also removed from the tab order and the whole page is much nicer to use now.