BUG: fix `Series.argsort` 
- [x] closes #42056
- [x] closes #12694

rendered whatsnew:
![Screen Shot 2021-09-18 at 13 56 52](https://user-images.githubusercontent.com/24256554/133888309-cdfdec3d-7bb4-4758-88b5-258b89f0105c.png)

