In the case of the public layout, the row element was originally there
so the content of the top links had a maximum width. Since now the body
has that maximum width, we no longer need the row element.
In the other layouts I guess the row elements were added because there
were float elements inside them. We can use a flexbox layout instead and
these elements are no longer necessary. This also makes the layout more
robust when there isn't enough space on one line for both the language
selector and the external links.
Note we're using `flex-grow: 1` to make one element appear on the left
of the screen and the other one on the right. It would be easier to use
`justify-content: space-between`. However, there's a bug in Internet
Explorer and old versions of Firefox; they include the
absolutely-positioned `::before` element we use to set the full width
background when calculating where to position the elements. The bug was
fixed in Firefox 52 (released in 2017).
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