Remove Erxes demo link (HTTP 502), update language/platform (#4012)

- ref. https://github.com/awesome-selfhosted/awesome-selfhosted/issues/3558
- `https://demo.erxes.io/ : HTTP 502`
- https://docs.erxes.io/docs/category/deployment

README.md

@@ -1999,7 +1999,7 @@ _Related: [Task Management & To-do Lists](#task-management--to-do-lists), [Softw
 
 - [Bugzilla](https://www.bugzilla.org/) - General-purpose bugtracker and testing tool originally developed and used by the Mozilla project. `MPL-2.0` `Perl`
 - [django-todo](http://django-todo.org/) - Pluggable, multi-user, multi-group, multi-list todo and ticketing system - a reusable app designed to be dropped into any existing Django project. ([Source Code](https://github.com/shacker/django-todo)) `BSD-3-Clause` `Python/Django`
-- [Erxes](https://erxes.io/install/) - Marketing, sales, and customer service platform designed to help businesses attract more engaged customers. ([Demo](https://demo.erxes.io/), [Source Code](https://github.com/erxes/erxes)) `GPL-3.0` `Javascript`
+- [Erxes](https://erxes.io/install/) - Marketing, sales, and customer service platform designed to help businesses attract more engaged customers. ([Source Code](https://github.com/erxes/erxes)) `GPL-3.0` `Docker`
 - [FreeScout](https://github.com/freescout-helpdesk/freescout) - Open source clone of Help Scout: email-based customer support application, help desk and shared mailbox. `AGPL-3.0` `PHP`
 - [GlitchTip](https://glitchtip.com) - Open source error-tracking app. GlitchTip collects errors reported by your app. ([Source Code](https://gitlab.com/glitchtip/glitchtip)) `MIT` `Python`
 - [Iguana](https://github.com/iguana-project/iguana) - Iguana is an open source issue management system with a kanban board. `CC-BY-SA-4.0` `Python/Docker`