message: docs: fix references in health checking docs
diff: @@ -59,11 +59,12 @@ Health check event logging
  --------------------------
  A per-healthchecker log of ejection and addition events can optionally be produced by Envoy by
  -specifying a log file path in `the HealthCheck config <envoy_api_field_core.HealthCheck.event_log_path>`.
  -The log is structured as JSON dumps of `HealthCheckEvent messages <envoy_api_msg_core.HealthCheckEvent>`.
  +specifying a log file path in :ref:`the HealthCheck config <envoy_api_field_core.HealthCheck.event_log_path>`.
  +The log is structured as JSON dumps of
  +:ref:`HealthCheckEvent messages <envoy_api_msg_data.core.v2alpha.HealthCheckEvent>`.
  -Envoy can be configured to log all health check failure events by setting the :ref:'always_log_health_check_failures
  -flag <envoy_api_field_core.HealthCheck.always_log_health_check_failures>' to true.
  +Envoy can be configured to log all health check failure events by setting the :ref:`always_log_health_check_failures
  +flag <envoy_api_field_core.HealthCheck.always_log_health_check_failures>` to true.
  Passive health checking
  -----------------------
  