message: docs: add relase note for degraded health
diff: @@ -25,6 +25,8 @@ Version history
  * tls: enabled TLS 1.3 on the server-side (non-FIPS builds).
  * router: added per-route configuration of :ref:`internal redirects <envoy_api_field_route.RouteAction.internal_redirect_action>`.
  * upstream: add hash_function to specify the hash function for :ref:`ring hash<envoy_api_msg_Cluster.RingHashLbConfig>` as either xxHash or `murmurHash2 <https://sites.google.com/site/murmurhash>`_. MurmurHash2 is compatible with std::hash in GNU libstdc++ 3.4.20 or above. This is typically the case when compiled on Linux and not macOS.
  +* upstream: added :ref:`degraded health value<arch_overview_load_balancing_degraded>` which allows
  + routing to certain hosts only when there are insufficient healthy hosts available.
  1.9.0
  ===============
  