Clarify that lazy_load_members in timeline isn't respected in /sync

data/api/client-server/definitions/room_event_filter.yaml

@@ -28,7 +28,8 @@ allOf:
       description: |-
         If `true`, enables lazy-loading of membership events. See
         [Lazy-loading room members](/client-server-api/#lazy-loading-room-members)
-        for more information. Defaults to `false`.
+        for more information. Defaults to `false`. Only applies to the `/messages`
+        endpoint, for `/sync` this should be specified in `StateFilter` instead.
     include_redundant_members:
       type: boolean
       description: |-
@@ -36,7 +37,8 @@ allOf:
         been sent to the client. Does not
         apply unless `lazy_load_members` is `true`. See
         [Lazy-loading room members](/client-server-api/#lazy-loading-room-members)
-        for more information. Defaults to `false`.
+        for more information. Defaults to `false`. Only applies to the `/messages`
+        endpoint, for `/sync` this should be specified in `StateFilter` instead.
     not_rooms:
       description: A list of room IDs to exclude. If this list is absent then no rooms
         are excluded. A matching room will be excluded even if it is listed in the `'rooms'`