Remove padding override on .ui .sha.label (go-gitea#35864)

Since upgrading to v1.25, I noticed the SHA labels have slightly
different padding than before. I can't pinpoint exactly which change it
was. Fix it by removing the padding override on `.ui .sha.label` and
make the one on`.ui.label` (`2px 6px`) take effect which matches 1.24
rendering.

Before:

<img width="135" height="172" alt="image"
src="https://github.com/user-attachments/assets/2781a854-be08-4a11-bde0-d3699b2b7454"
/>

After:

<img width="139" height="162" alt="image"
src="https://github.com/user-attachments/assets/5c864fa3-c1f9-4452-ae58-5411dd445865"
/>

Author: silverwind

web_src/css/base.css

@@ -626,7 +626,6 @@ img.ui.avatar,
   font-family: var(--fonts-monospace);
   font-size: 13px;
   font-weight: var(--font-weight-normal);
-  padding: 3px 5px;
   flex-shrink: 0;
 }