Docs: Update link to Kubernetes controller documentation. (#13947)

Co-authored-by: DongHo Jung <[email protected]>

Author: k8s-infra-cherrypick-robot

docs/how-it-works.md

@@ -64,7 +64,7 @@ To prevent this situation to happen, the Ingress-Nginx Controller optionally exp
 This webhook appends the incoming ingress objects to the list of ingresses, generates the configuration and calls nginx to ensure the configuration has no syntax errors.
 
 [0]: https://github.com/openresty/lua-nginx-module/pull/1259
-[1]: https://coreos.com/kubernetes/docs/latest/replication-controller.html#the-reconciliation-loop-in-detail
+[1]: https://kubernetes.io/docs/concepts/architecture/controller/#controller-pattern
 [2]: https://godoc.org/k8s.io/client-go/informers#NewFilteredSharedInformerFactory
 [3]: https://godoc.org/k8s.io/client-go/tools/cache#ResourceEventHandlerFuncs
 [4]: https://github.com/kubernetes/ingress-nginx/blob/main/internal/task/queue.go#L38