Non-admin user tries to delete non-existing result 401

## Describe the bug

Non-admin users try to delete the non-existing users. Then the API request returns a 401 HTTP status code.
```
curl -u user:password DELETE 'https://localhost:9200/graph/v1.0/users/random-uuid' \
```

## Expected behavior
The HTTP status code should be 404. Forbidden rather than 401 Unauthorized

## Actual behavior
Return 401 Unauthorized