Backport #30215 by @silverwind
On the labels list, This `left` class caused the dropdown content to
flash on page load until JS had hidden it. Remove it as I see no purpose
to it.
<img width="215" alt="image"
src="https://github.com/go-gitea/gitea/assets/115237/9e1de97f-dd89-41e0-9229-5c4a786ba762">
Co-authored-by: silverwind <me@silverwind.io>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>
(cherry picked from commit 3ff4a6936b5ee05b3df945c466285de47ea87ef2)
94fc99c217