Remove age_ts from reference hash calculation (#1536)

* Remove age_ts from reference hash calculation

Signed-off-by: Michael Kohler <me@michaelkohler.info>

* Add newsfragment

* Fix newsfragment number

* Update changelogs/server_server/newsfragments/1536.clarification

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

---------

Signed-off-by: Michael Kohler <me@michaelkohler.info>
Co-authored-by: Travis Ralston <travpc@gmail.com>

changelogs/server_server/newsfragments/1536.clarification

@@ -0,0 +1 @@
+Remove extraneous `age_ts` field from the reference hash calculation section.

content/server-server-api.md

@@ -1270,7 +1270,7 @@ specification](/rooms) for more information. It is
 calculated as follows.
 
 1.  The event is put through the redaction algorithm.
-2.  The `signatures`, `age_ts`, and `unsigned` properties are removed
+2.  The `signatures` and `unsigned` properties are removed
     from the event, if present.
 3.  The event is converted into [Canonical
     JSON](/appendices#canonical-json).