UX: Minor what's new card improvements (#36797)

* Add spacing between month groups
* Make month title bigger than item title

app/assets/stylesheets/admin/dashboard.scss

@@ -735,6 +735,12 @@
   }
 }
 
+.admin-new-features {
+  &__group {
+    margin-bottom: 1em;
+  }
+}
+
 .admin-new-feature-item__header-experimental {
   color: var(--tertiary);
   background-color: var(--tertiary-very-low);

frontend/discourse/admin/components/dashboard-new-features.gjs

@@ -100,10 +100,12 @@ export default class DashboardNewFeatures extends Component {
         </div>
         {{#each this.groupedNewFeatures as |groupedFeatures|}}
           <AdminConfigAreaCard
-            @translatedHeading={{groupedFeatures.date}}
             class="admin-new-features__group"
             data-new-features-group={{groupedFeatures.date}}
           >
+            <:header>
+              <h2>{{groupedFeatures.date}}</h2>
+            </:header>
             <:content>
               {{#each groupedFeatures.features as |feature|}}
                 <DashboardNewFeatureItem @item={{feature}} />