remove mydrive demo link (error 503)

- ref. https://github.com/awesome-selfhosted/awesome-selfhosted/issues/2266

README.md

@@ -875,7 +875,7 @@ _Related: [Groupware](#groupware)_
 
 - [Git Annex](https://git-annex.branchable.com/) - File synchronization between computers, servers, external drives. ([Source Code](https://git.joeyh.name/index.cgi/git-annex.git/)) `GPL-3.0` `Haskell`
 - [Kinto](https://kinto.readthedocs.org) - Kinto is a minimalist JSON storage service with synchronisation and sharing abilities. ([Source Code](https://github.com/Kinto)) `Apache-2.0` `Python`
-- [myDrive](https://github.com/subnub/myDrive) - Fully featured online storage solution, upload/download files, photo/video viewer, and more, all through the web client. ([Demo](https://mydrive-demo.herokuapp.com/)) `GPL-3.0` `Nodejs`
+- [myDrive](https://github.com/subnub/myDrive) - Fully featured online storage solution, upload/download files, photo/video viewer, and more, all through the web client. `GPL-3.0` `Nodejs`
 - [Nextcloud](https://nextcloud.com/) - Access and share your files, calendars, contacts, mail and [more](https://apps.nextcloud.com/) from any device, on your terms. ([Demo](https://try.nextcloud.com/), [Source Code](https://github.com/nextcloud/server)) `AGPL-3.0` `PHP`
 - [OpenSSH SFTP server](https://www.openssh.com/) - Secure File Transfer Program. ([Source Code](https://cvsweb.openbsd.org/cgi-bin/cvsweb/src/usr.bin/ssh/)) `BSD-2-Clause` `C`
 - [ownCloud](https://owncloud.org/) - All-in-one solution for saving, synchronizing, viewing, editing and sharing files, calendars, address books and more. ([Source Code](https://github.com/owncloud/core), [Clients](https://github.com/owncloud/core/wiki/Apps)) `AGPL-3.0` `PHP`