Update proposals/2403-knock.md

Co-authored-by: Richard van der Hoff <1389908+richvdh@users.noreply.github.com>

proposals/2403-knock.md

@@ -346,7 +346,7 @@ homeserver. The response contains `StrippedStateEvent`s with room metadata
 The event types that can be sent here should match those of the `/sync`
 extensions mentioned above.
 
-This is loosely based off of the
+This is loosely based on the
 [federated invite](https://matrix.org/docs/spec/server_server/r0.1.4#put-matrix-federation-v2-invite-roomid-eventid)
 request content.
 ```json