Fix active item in tab menu (#30690)

Before, item would also resize on hover because of font weight:
<img width="381" alt="Screenshot 2024-04-25 at 01 28 53"
src="https://github.com/go-gitea/gitea/assets/115237/4f3291fc-90be-4d66-ae8b-3c2f763cb956">

After:
<img width="381" alt="Screenshot 2024-04-25 at 01 28 40"
src="https://github.com/go-gitea/gitea/assets/115237/06145bf2-1ddd-4171-9217-d92c100ea405">

Co-authored-by: Giteabot <teabot@gitea.io>

web_src/css/modules/menu.css

@@ -403,7 +403,7 @@
   background: var(--color-body);
   border-top-width: 1px;
   border-color: var(--color-secondary);
-  font-weight: var(--font-weight-medium);
+  color: var(--color-text-dark);
   margin-bottom: -1px;
   border-radius: 0.28571429rem 0.28571429rem 0 0 !important;
 }