rest/client: fix comment lint error (#465)

Signed-off-by: James Hillyerd <james@hillyerd.com>

pkg/rest/client/apiv1_client_opts.go

@@ -11,6 +11,7 @@ type options struct {
 	timeout   time.Duration
 }
 
+// Option can apply itself to the private options type.
 type Option interface {
 	apply(*options)
 }