message: docs: add back version_history line
  This got deleted accidentally in
diff: @@ -24,6 +24,7 @@ Version history
  * cli: added --config-yaml flag to the Envoy binary. When set its value is interpreted as a yaml
  representation of the bootstrap config and overrides --config-path.
  * cluster: Add :ref:`option <envoy_api_field_Cluster.close_connections_on_host_health_failure>`
  + to close tcp_proxy upstream connections when health checks fail.
  * cluster: Add :ref:`option <envoy_api_field_Cluster.drain_connections_on_host_removal>` to drain
  connections from hosts after they are removed from service discovery, regardless of health status.
  * health check: added ability to set :ref:`additional HTTP headers
  