fix(platform-objects): drop empty group_apps nav contribution left by #1771

#1771 moved both marketplace entries out to cloud-connection's plugins
but left the now-empty contribution behind, tripping the
SETUP_NAV_CONTRIBUTIONS test ('items.length > 0') and turning main CI
red. The group_apps shell anchor stays in setup.app.ts and is filled
entirely by capability plugins.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: os-zhuang

packages/platform-objects/src/apps/setup-nav.contributions.ts

@@ -38,13 +38,9 @@ export const SETUP_NAV_CONTRIBUTIONS: NavigationContribution[] = [
       { id: 'nav_system_overview', type: 'dashboard', label: 'System Overview', dashboardName: 'system_overview', icon: 'activity' },
     ],
   },
-  {
-    app: 'setup',
-    group: 'group_apps',
-    priority: BASE_PRIORITY,
-    items: [
-    ],
-  },
+  // No group_apps contribution left here — both marketplace entries moved
+  // out (see header note); the group_apps shell anchor in setup.app.ts is
+  // filled entirely by capability plugins now.
   {
     app: 'setup',
     group: 'group_people_org',