Remove shorturl (unmaintained since 2021, website down) (#4061)

- https://git.mills.io/prologic/shorturl/commits/branch/master
- `https://url.mills.io : HTTP 503`
- ref. #3558

README.md

@@ -2055,7 +2055,6 @@ _Related: [Task Management & To-do Lists](#task-management--to-do-lists), [Softw
 - [ReducePy](https://github.com/abdullahselek/ReducePy) - URL shortener service using Tornado and Redis runs on Docker and Kubernetes. `MIT` `Python`
 - [schort](https://github.com/sqozz/schort) - No login, no javascript, just short links. `CC0-1.0` `Python`
 - [Shlink](https://shlink.io) - URL shortener with REST API and command line interface. Includes official progressive web application and docker images. ([Source Code](https://github.com/shlinkio/shlink), [Clients](https://shlink.io/apps)) `MIT` `PHP`
-- [shorturl](https://git.mills.io/prologic/shorturl) - Simple URL shortener with very tiny URLs. ([Demo](https://url.mills.io)) `MIT` `Go`
 - [Short{Paste}](https://github.com/adyanth/shortpaste) - A Go based URL shortener, pastebin and file uploader. `MIT` `Docker`
 - [Simple-URL-Shortener](https://github.com/azlux/Simple-URL-Shortener) - KISS URL shortener, public or private (with account). Minimalist and lightweight. No dependencies. ([Demo](https://u.azlux.fr)) `MIT` `PHP`
 - [Simply Shorten](https://gitlab.com/draganczukp/simply-shorten) - A simple URL shortener that just shortens links. `MIT` `Java`