fix(rbac): remove rate limiting bypass permission from dashboard admin

- Removed Permissions.rateLimitingBypass from _dashboardAdminPermissions set
- Ensures dashboard admins are subject to rate limiting measures

Author: fulleni

lib/src/rbac/role_permissions.dart

@@ -39,7 +39,6 @@ final Set<String> _dashboardPublisherPermissions = {
 
 final Set<String> _dashboardAdminPermissions = {
   ..._dashboardPublisherPermissions,
-  Permissions.rateLimitingBypass,
   Permissions.topicCreate,
   Permissions.topicUpdate,
   Permissions.topicDelete,