Unable to delete Duplicate Tags

### Expected

Duplicate Tags should not be showed in Tags list.
OR
One of Duplicate Tags can be deleted.

### Observed

One of Duplicate Tags can not be deleted. I have two "debug" tag. For the first one, "Delete Tag" button is useless, the second one can be deleted.
The behavior of tags modification is strange, as the gif shows,

### Reproduced

I don't know how this strange tag appeared, maybe error occurs in sync procedure.
1. click menu
2. click Tags list Edit
3. click Trash button

### Where did you see the bug

- System Make:
- System Model:
- OS: Windows
- OS version: Windows 10
- Browser (if applicable):
- Browser version (if applicable):
- Simplenote app version: 2.21.0

No source files, tests, or entry points are named. Start by reproducing duplicate-tag editing and deletion on Windows 10 with app version 2.21.0, then inspect the tag list and sync behavior; done means duplicate tags no longer persist or the affected duplicate can be deleted.

Written by the indexing model from the issue text.