Remove dead link (#3346)

https://www.sakaiproject.org/try-sakai is not reachable

README.md

@@ -1124,7 +1124,6 @@ Tools and software to help with education and learning.
 - [OpenOLAT](https://www.openolat.com/?lang=en) - OpenOLAT is a web-based learning management system for teaching, education, assessment and communication. ([Demo](https://learn.olat.com), [Source Code](https://github.com/OpenOLAT/OpenOLAT)) `Apache-2.0` `Java`
 - [RELATE](https://documen.tician.de/relate/) - RELATE is a web-based courseware package, includes features such as: flexible rules, statistics, multi-course support, class calendar. ([Source Code](https://github.com/inducer/relate)) `MIT` `Python`
 - [RosarioSIS](https://www.rosariosis.org/) - RosarioSIS, free Student Information System for school management. ([Demo](https://www.rosariosis.org/demo/), [Source Code](https://gitlab.com/francoisjacquet/rosariosis/)) `GPL-2.0` `PHP`
-- [Sakai](https://www.sakaiproject.org/) - The Sakai project provides a flexible and feature-rich environment for teaching, learning, research and other collaboration. ([Demo](https://www.sakaiproject.org/try-sakai), [Source Code](https://github.com/sakaiproject/sakai)) `ECL-2.0` `Java`
 - [Vocascan](https://vocascan.com/) - A highly configurable vocabulary trainer. ([Source Code](https://github.com/vocascan/vocascan-server), [Clients](https://github.com/vocascan/vocascan-desktop)) `Apache-2.0` `Nodejs`