Update toc.yml

Author: genlin

support/entra/entra-id/toc.yml

@@ -280,6 +280,8 @@
      href: app-integration/graph-api-error-handling-invoke-restmethod.md
    - name: Troubleshoot Authorization RequestDenied error
      href: app-integration/troubleshoot-authorization-requestdenied-graph-api.md
+   - name: 403 error when adding a user to a group
+     href: users-groups-entra-apis/authorization-requestdenied-403-error-add-user-group.md
    - name: 404 error when managing objects
      href: app-integration/404-not-found-error-manage-objects-microsoft-graph.md
    - name: Use managed identities to call Graph APIs in VB.Net and C#