message: tracers: fix typo s/lightstep/Zipkin/
diff: @@ -27,7 +27,7 @@ Tracing::HttpTracerPtr ZipkinTracerFactory::createHttpTracerTyped(
  }
  /**
  - * Static registration for the lightstep tracer. @see RegisterFactory.
  + * Static registration for the Zipkin tracer. @see RegisterFactory.
  */
  REGISTER_FACTORY(ZipkinTracerFactory, Server::Configuration::TracerFactory);
  