Add missing bracket (#2224)

changelogs/client_server/newsfragments/2224.clarification

@@ -0,0 +1 @@
+Fix various typos throughout the specification.

data/api/client-server/old_sync.yaml

@@ -324,7 +324,7 @@ paths:
         This endpoint was deprecated in r0 of this specification. Clients
         should instead call the
         [/rooms/{roomId}/event/{eventId}](/client-server-api/#get_matrixclientv3roomsroomideventeventid) API
-        or the [/rooms/{roomId}/context/{eventId](/client-server-api/#get_matrixclientv3roomsroomidcontexteventid) API.
+        or the [/rooms/{roomId}/context/{eventId}](/client-server-api/#get_matrixclientv3roomsroomidcontexteventid) API.
       operationId: getOneEvent
       security:
         - accessTokenQuery: []