Backport #31204 by @silverwind
Using `.segment` on the project columns is a major abuse of that class,
so remove it and instead set the border-radius directly on it.
Fixes: https://github.com/go-gitea/gitea/issues/31129
Co-authored-by: silverwind <me@silverwind.io>
(cherry picked from commit 298d05df3b79634a0364926f34fb02b73d442c31)