Update RPM notes for 1.5.23 hardening

Author: eldryoth

packaging/rpm/fluxheim.spec

@@ -159,6 +159,8 @@ fi
   origin-fill budgets.
 - Expose origin-protection rollout in cache status and metrics.
 - Include origin-protection state in cache-key/cache-lookup release gates.
+- Consolidate cache-fill concurrency limiters so slice-fill, peer-fill, and
+  origin-fill budgets share one hardened implementation.
 
 * Sun Jun 14 2026 Fluxheim Maintainers <1921261+eldryoth@users.noreply.github.com> - 1.5.22-1
 - Continue cache/load-balancer crate-boundary preparation.