cutting 1.9 release (#5366)

Risk Level: n/a
Testing: n/a
Docs Changes: 1.9!
Release Notes: They're official
Deprecated: 1.8 ;-)

Signed-off-by: Alyssa Wilk <alyssar@chromium.org>

DEPRECATED.md

@@ -6,7 +6,7 @@ As of release 1.3.0, Envoy will follow a
 The following features have been DEPRECATED and will be removed in the specified release cycle.
 A logged warning is expected for each deprecated item that is in deprecation window.
 
-## Version 1.9.0 (pending)
+## Version 1.9.0
 
 * Order of execution of the network write filter chain has been reversed. Prior to this release cycle it was incorrect, see [#4599](https://github.com/envoyproxy/envoy/issues/4599). In the 1.9.0 release cycle we introduced `bugfix_reverse_write_filter_order` in [lds.proto] (https://github.com/envoyproxy/envoy/blob/master/api/envoy/api/v2/lds.proto) to temporarily support both old and new behaviors. Note this boolean field is deprecated.
 * Order of execution of the HTTP encoder filter chain has been reversed. Prior to this release cycle it was incorrect, see [#4599](https://github.com/envoyproxy/envoy/issues/4599). In the 1.9.0 release cycle we introduced `bugfix_reverse_encode_order` in [http_connection_manager.proto] (https://github.com/envoyproxy/envoy/blob/master/api/envoy/config/filter/network/http_connection_manager/v2/http_connection_manager.proto) to temporarily support both old and new behaviors. Note this boolean field is deprecated.

VERSION

@@ -1 +1 @@
-1.9.0-dev
+1.9.0

docs/root/intro/version_history.rst

@@ -1,7 +1,7 @@
 Version history
 ---------------
 
-1.9.0 (pending)
+1.9.0
 ===============
 * access log: added a :ref:`JSON logging mode <config_access_log_format_dictionaries>` to output access logs in JSON format.
 * access log: added dynamic metadata to access log messages streamed over gRPC.