Do not allow setting m.push_rules account data directly. (#1763)

* Do not allow setting m.push_rules account data directly.

* Newsfragment

* Update 1763.clarification

Co-authored-by: Travis Ralston <travpc@gmail.com>

* add change notice

Co-authored-by: Travis Ralston <travpc@gmail.com>

* clarify read status

Co-authored-by: Travis Ralston <travpc@gmail.com>

* Fix link for push rules.

* Refer to the error response

---------

Co-authored-by: Travis Ralston <travpc@gmail.com>

changelogs/client_server/newsfragments/1763.clarification

@@ -0,0 +1 @@
+Clarify that the `m.push_rules` account data type cannot be set using the `/account_data` API, as per [MSC4010](https://github.com/matrix-org/matrix-spec-proposals/pull/4010).

content/client-server-api/modules/account_data.md

@@ -26,6 +26,15 @@ These events can also be received in a `/events` response or in the
 
 #### Server Behaviour
 
-Servers MUST reject clients from setting account data for event types
-that the server manages. Currently, this only includes
-[m.fully\_read](#mfully_read).
+Servers MUST reject setting account data for event types
+that the server manages by using a 405 error response.
+Currently, this only includes [`m.fully_read`](#mfully_read)
+and [`m.push_rules`](#push-rules-events). This applies to
+both global and room-specific account data.
+
+{{% boxes/note %}}
+{{% changed-in v="1.10" %}} `m.push_rules` was added to the rejection
+list.
+{{% /boxes/note %}}
+
+Servers must allow clients to read the above event types as normal.