bug (adwaita): closing tabs doesn't always relayout the tab overview correctly

[FantomeBeignet]

Closing the last tab in the tab overview causes the remaining tabs to get centered in the window, which I expect is the desired behavior. However, closing a tab that is not the last one causes the tabs to get left aligned, which doesn't look as good.

Another thing that doesn't look like desired behavior: when the tabs occupy more than one line, the second line of tabs is left aligned and not centered. Maybe this is intended, but I would expect them to be centered (and I think it would look better as well).