Fix vitessio#16565

This did not have a practical impact but was obviously
wrong

Signed-off-by: Matt Lord <mattalord@gmail.com>

go/vt/vtctl/workflow/materializer.go

@@ -618,7 +618,7 @@ func primaryVindexesDiffer(ms *vtctldatapb.MaterializeSettings, source, target *
  // If neither source nor target have any vindexes, treat the answer to
  // the question as trivially false.
  if len(sColumnVindexes) == 0 && len(tColumnVindexes) == 0 {
- return true
+ return false
  }
 
  sPrimaryVindex := sColumnVindexes[0]