remove multiClusterCidr flag

The MultiClusterCidr has been removed upstream (starting from 1.28) so the flag doesnt make sense anymore.

The mechanism is kept because the feature should be implemented similarly in a dedicated controller at some point.

main.go

@@ -94,7 +94,6 @@ type CmdLineOpts struct {
 	iptablesForwardRules      bool
 	netConfPath               string
 	setNodeNetworkUnavailable bool
-	useMultiClusterCidr       bool
 }
 
 var (
@@ -131,7 +130,6 @@ func init() {
 	flannelFlags.BoolVar(&opts.iptablesForwardRules, "iptables-forward-rules", true, "add default accept rules to FORWARD chain in iptables")
 	flannelFlags.StringVar(&opts.netConfPath, "net-config-path", "/etc/kube-flannel/net-conf.json", "path to the network configuration file")
 	flannelFlags.BoolVar(&opts.setNodeNetworkUnavailable, "set-node-network-unavailable", true, "set NodeNetworkUnavailable after ready")
-	flannelFlags.BoolVar(&opts.useMultiClusterCidr, "use-multi-cluster-cidr", false, "use MultiClusterCIDR API (alpha)")
 
 	log.InitFlags(nil)
 
@@ -177,7 +175,7 @@ func newSubnetManager(ctx context.Context) (subnet.Manager, error) {
 			opts.kubeAnnotationPrefix,
 			opts.netConfPath,
 			opts.setNodeNetworkUnavailable,
-			opts.useMultiClusterCidr)
+			false)
 	}
 
 	cfg := &etcd.EtcdConfig{