Remove extra preposition in room version 11 description of redactions (#1848)

Signed-off-by: Johannes Marbach <n0-0ne+github@mailbox.org>

changelogs/room_versions/newsfragments/1848.clarification

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

content/rooms/v11.md

@@ -72,7 +72,7 @@ The `redacts` property of `m.room.redaction` events is moved from a top-level
 event property to a property under the event `content`.
 
 For backwards-compatibility with older clients, servers should add a `redacts` property
-to the top level of `m.room.redaction` events in when serving such events over the
+to the top level of `m.room.redaction` events when serving such events over the
 Client-Server API.
 
 For improved compatibility with newer clients, servers should add a `redacts` property