example data [nfc]: Remove incorrect assertion for message move

This does not correctly catch the case when
`origTopic='topic'`, and
`newTopic=origStreamId=newStreamId=null`.

Instead, remove it and rely on the assertions from
UpdateMessageMoveData's constructor.

Signed-off-by: Zixuan James Li <[email protected]>

Author: PIG208

test/example_data.dart

@@ -677,8 +677,6 @@ UpdateMessageEvent _updateMessageMoveEvent(
 }) {
   _checkPositive(origStreamId, 'stream ID');
   _checkPositive(newStreamId, 'stream ID');
-  assert(newTopic != origTopic
-         || (newStreamId != null && newStreamId != origStreamId));
   assert(messageIds.isNotEmpty);
   return UpdateMessageEvent(
     id: 0,