barLevel: Stop capping border-width at 1 pixel

barLevel: Stop capping border-width at 1 pixel

I can't think of a reason why limiting the border to a maximum
would make any sense.

The original intention was probably to set a minimum border width
to avoid having to deal with border/no-border complexity in the code,
but as cairo accepts a line width of 0, it just works.

However limiting the size to the overall height seems reasonable,
as at that size a bigger height and different fill color can
achieve the same effect without requires special handling of
other values like the radius.

Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/2994>