The activities button doesn't have an icon, which makes its horizontal
padding appear a bit smaller than the padding of most other items in the
panel.
We're going to indicate hover and focus of items in the panel using a
pill-shaped background color, which means the padding of those items
will get more visible. So give the activities button a special treatment
and slightly increase its padding to make sure the new indicator will
look good.
Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/1397>
a44686affe