Style fomantic grey labels (#29458)

Fomantic grey labels in the dashboard repo lists were showing original
fomantic colors, fixed that. Also slightly tweaked the light theme
colors so it uses same opacity values as dark theme.

<img width="165" alt="Screenshot 2024-03-07 at 21 06 23"
src="https://github.com/go-gitea/gitea/assets/115237/72744d6f-2ee1-4e5d-8ba0-b482a446f535">
<img width="167" alt="Screenshot 2024-03-07 at 21 06 00"
src="https://github.com/go-gitea/gitea/assets/115237/1ba93775-e5a9-4b28-b90f-59c1e9199687">

web_src/css/base.css

@@ -1448,7 +1448,9 @@ strong.attention-caution, span.attention-caution {
 }
 
 .ui.label,
-.ui.menu .item > .label {
+.ui.menu .item > .label,
+.ui.grey.labels .label,
+.ui.ui.ui.grey.label {
   background: var(--color-label-bg);
   color: var(--color-label-text);
 }

web_src/css/themes/theme-gitea-light.css

@@ -228,9 +228,9 @@
   --color-nav-hover-bg: #ebebeb;
   --color-nav-text: var(--color-text);
   --color-label-text: var(--color-text);
-  --color-label-bg: #cacaca5b;
-  --color-label-hover-bg: #cacacaa0;
-  --color-label-active-bg: #cacacaff;
+  --color-label-bg: #9d9d9d4b;
+  --color-label-hover-bg: #9d9d9da0;
+  --color-label-active-bg: #9d9d9dff;
   --color-accent: var(--color-primary-light-1);
   --color-small-accent: var(--color-primary-light-6);
   --color-active-line: #fffbdd;