deploy/static: use kube-system as the default election namespace

kube-system is always present in every cluster, unlike the
"cert-manager" namespace. The reason we want a central namespace is that
we want to avoid mistakenly creating two replicas (in the same pod, or
in different pods across namespaces) of openshift-routes.

deploy/static/cert-manager-openshift-routes.yaml

@@ -114,6 +114,7 @@ spec:
           image: "ghcr.io/cert-manager/cert-manager-openshift-routes:${RELEASED_VERSION}"
           args:
             - -v=5
+            - -leader-election-namespace=kube-system
           ports:
             - containerPort: 6060
               name: readiness