Fix action runner offline label padding (#29691)

Before:

The `offline` padding is `calc(.833em - 1px)` from `basic` CSS class,
but `idle` padding is `6px`.

<img width="1035" alt="image"
src="https://github.com/go-gitea/gitea/assets/37034805/ccb42615-20d7-4032-a805-40cd9643012d">

After:

<img width="1035" alt="image"
src="https://github.com/go-gitea/gitea/assets/37034805/d6af99c8-76cb-4850-96d6-5289b06e1ca8">

templates/shared/actions/runner_list.tmpl

@@ -68,7 +68,7 @@
 					{{range .Runners}}
 					<tr>
 						<td>
-							<span class="ui {{if .IsOnline}}green{{else}}basic{{end}} label">{{.StatusLocaleName ctx.Locale}}</span>
+							<span class="ui {{if .IsOnline}}green{{end}} label">{{.StatusLocaleName ctx.Locale}}</span>
 						</td>
 						<td>{{.ID}}</td>
 						<td><p data-tooltip-content="{{.Description}}">{{.Name}}</p></td>