Note LoggingContext signature change incompatibility in 1.32.0 (#9859)

1.32.0 also introduced an incompatibility with Synapse modules that make use of `synapse.logging.context.LoggingContext`, such as [synapse-s3-storage-provider](https://github.com/matrix-org/synapse-s3-storage-provider).

This PR adds a note to the 1.32.0 changelog and upgrade notes about it.

CHANGES.md

@@ -2,10 +2,10 @@ Synapse 1.32.1 (2021-04-21)
 ===========================
 This release fixes [a regression](https://github.com/matrix-org/synapse/issues/9853)
-in Synapse 1.32.0 that caused connected Prometheus instances to become unstable. If you
-ran Synapse 1.32.0 with Prometheus metrics, first upgrade to Synapse 1.32.1 and follow
-[these instructions](https://github.com/matrix-org/synapse/pull/9854#issuecomment-823472183)
-to clean up any excess writeahead logs.
+in Synapse 1.32.0 that caused connected Prometheus instances to become unstable. 
+
+However, as this release is still subject to the `LoggingContext` change in 1.32.0,
+it is recommended to remain on or downgrade to 1.31.0.
 Bugfixes
 --------
@@ -18,7 +18,14 @@ Synapse 1.32.0 (2021-04-20)
 **Note:** This release introduces [a regression](https://github.com/matrix-org/synapse/issues/9853)
 that can overwhelm connected Prometheus instances. This issue was not present in
-1.32.0rc1, and is fixed in 1.32.1. See the changelog for 1.32.1 above for more information.
+1.32.0rc1. If affected, it is recommended to downgrade to 1.31.0 in the meantime, and 
+follow [these instructions](https://github.com/matrix-org/synapse/pull/9854#issuecomment-823472183)
+to clean up any excess writeahead logs.
+
+**Note:** This release also mistakenly included a change that may affected Synapse 
+modules that import `synapse.logging.context.LoggingContext`, such as
+[synapse-s3-storage-provider](https://github.com/matrix-org/synapse-s3-storage-provider).
+This will be fixed in a later Synapse version.
 **Note:** This release requires Python 3.6+ and Postgres 9.6+ or SQLite 3.22+.

UPGRADE.rst

@@ -93,11 +93,11 @@ Regression causing connected Prometheus instances to become overwhelmed
 
 This release introduces `a regression <https://github.com/matrix-org/synapse/issues/9853>`_
 that can overwhelm connected Prometheus instances. This issue is not present in
-Synapse v1.32.0rc1, and is fixed in Synapse v1.32.1.
+Synapse v1.32.0rc1.
 
-If you have been affected, please first upgrade to a more recent Synapse version.
-You then may need to remove excess writeahead logs in order for Prometheus to recover.
-Instructions for doing so are provided
+If you have been affected, please downgrade to 1.31.0. You then may need to
+remove excess writeahead logs in order for Prometheus to recover. Instructions
+for doing so are provided
 `here <https://github.com/matrix-org/synapse/pull/9854#issuecomment-823472183>`_.
 
 Dropping support for old Python, Postgres and SQLite versions