Update registry.k8s.io/ingress-nginx/kube-webhook-certgen Docker tag to v1.4.3

This MR contains the following updates:

Package	Type	Update	Change
registry.k8s.io/ingress-nginx/kube-webhook-certgen		patch	v1.4.1 -> v1.4.3
registry.k8s.io/ingress-nginx/kube-webhook-certgen	ironbank-docker	patch	v1.4.1 -> v1.4.3
registry.k8s.io/ingress-nginx/kube-webhook-certgen	stage	patch	v1.4.1 -> v1.4.3

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