Fix label-list rendering in timeline, decrease gap (#30342) (#30380)

Fix label-list rendering in timeline, decrease gap (#30342) (#30380)

Backport #30342 by @silverwind

Not sure exactly when this regressed, but has been a while I think.

Before:

<img width="895" alt="Screenshot 2024-04-08 at 22 46 50"
src="https://github.com/go-gitea/gitea/assets/115237/9b1788f8-017e-4fe1-8ab9-938e0d76fb41">

After:

<img width="689" alt="Screenshot 2024-04-08 at 23 00 58"
src="https://github.com/go-gitea/gitea/assets/115237/90193df9-5c24-4a1a-96fe-3d4e8392063c">

Co-authored-by: silverwind <me@silverwind.io>