Remove Open Conference Systems (OCS) (retired) (#3533)

> Retired Software
> This page lists the applications that we have retired. These applications should not be used. They will no longer receive security updates or technical support.

Co-authored-by: nodiscc <nodiscc@gmail.com>

README.md

@@ -651,7 +651,6 @@ Software for submission of [abstracts](https://en.wikipedia.org/wiki/Abstract_ma
 - [Conference Organizing Distribution (COD)](http://usecod.com/) - Create conference and event websites built on top of Drupal. ([Source Code](https://git.drupalcode.org/project/cod)) `GPL-1.0` `PHP`
 - [frab](https://frab.github.io/frab/) - Web-based conference planning and management system. It helps to collect submissions, to manage talks and speakers and to create a schedule. ([Source Code](https://github.com/frab/frab)) `MIT` `Ruby`
 - [indico](https://getindico.io/) - A feature-rich event management system, made @ CERN, the place where the Web was born. ([Demo](https://sandbox.getindico.io/), [Source Code](https://github.com/indico/indico)) `MIT` `Python`
-- [Open Conference Systems (OCS)](https://pkp.sfu.ca/ocs/) - Free Web publishing tool that will create a complete Web presence for your scholarly conference. ([Source Code](https://github.com/pkp/ocs)) `GPL-1.0` `PHP`
 - [osem](https://osem.io/) - Event management tailored to free Software conferences. ([Demo](https://demo.osem.io/), [Source Code](https://github.com/openSUSE/osem)) `MIT` `Ruby`
 - [pretalx](https://pretalx.org) - Web-based event management, including running a Call for Papers, reviewing submissions, and scheduling talks. Exports and imports for various related tools. ([Source Code](https://github.com/pretalx/pretalx)) `Apache-2.0` `Python`