chore: Add matrix-org#2357 in `changelogs/.

Author: Hywan

changelogs/client_server/newsfragments/2357.clarification

@@ -0,0 +1,11 @@
+Fixes a typo in `/rooms/{roomId}/relations/{eventId}`.
+
+The specification says:
+
+> The pagination token to start returning results from. If not supplied, results start at the most recent topological event known to the server.
+>
+> Can be a `next_batch` or `prev_batch` token from a previous call, or a returned `start` token from `/messages`, or a `next_batch` token from `/sync`.
+
+The last part is wrong. It should be:
+
+> … or a `prev_batch` token from `/sync`.