Call out upgrade notes in README

CHANGES.md

@@ -1,6 +1,10 @@
 # Synapse 1.88.0rc1 (2023-07-11)
 
-Note that the minimum supported version of Python is now 3.8, as Python 3.7 is now [end-of-life](https://devguide.python.org/versions/).
+This release
+ - raises the minimum supported version of Python to 3.8, as Python 3.7 is now [end-of-life](https://devguide.python.org/versions/), and
+ - removes deprecated config options related to worker deployment.
+
+See [the upgrade notes](https://github.com/matrix-org/synapse/blob/release-v1.88/docs/upgrade.md#upgrading-to-v1880) for more information.
 
 ### Features
 
@@ -19,8 +23,8 @@ Note that the minimum supported version of Python is now 3.8, as Python 3.7 is n
 
 ### Deprecations and Removals
 
+- **Remove deprecated `worker_replication_host`, `worker_replication_http_port` and `worker_replication_http_tls` configuration options.** See the [upgrade notes](https://github.com/matrix-org/synapse/blob/release-v1.88/docs/upgrade.md#removal-of-worker_replication_-settings) for more details. ([\#15860](https://github.com/matrix-org/synapse/issues/15860))
 - Remove support for Python 3.7 and hence for Debian Buster. ([\#15851](https://github.com/matrix-org/synapse/issues/15851), [\#15892](https://github.com/matrix-org/synapse/issues/15892), [\#15893](https://github.com/matrix-org/synapse/issues/15893))
-- Remove deprecated `worker_replication_host`, `worker_replication_http_port` and `worker_replication_http_tls` configuration options. ([\#15860](https://github.com/matrix-org/synapse/issues/15860))
 
 ### Internal Changes