Bump konnectivity-client to v0.0.12

vendor/sigs.k8s.io/apiserver-network-proxy/konnectivity-client/pkg/client/client.go

@@ -51,6 +51,12 @@ type grpcTunnel struct {
 	connsLock       sync.RWMutex
 }
 
+type clientConn interface {
+	Close() error
+}
+
+var _ clientConn = &grpc.ClientConn{}
+
 // CreateSingleUseGrpcTunnel creates a Tunnel to dial to a remote server through a
 // gRPC based proxy service.
 // Currently, a single tunnel supports a single connection, and the tunnel is closed when the connection is terminated
@@ -79,7 +85,7 @@ func CreateSingleUseGrpcTunnel(address string, opts ...grpc.DialOption) (Tunnel,
 	return tunnel, nil
 }
 
-func (t *grpcTunnel) serve(c *grpc.ClientConn) {
+func (t *grpcTunnel) serve(c clientConn) {
 	defer c.Close()
 
 	for {