Enhancement: Update ownCloud Web to v5.5.0-rc.6

Tags: web

We updated ownCloud Web to v5.5.0-rc.6. Please refer to the changelog (linked) for details on the web release.

https://github.com/owncloud/web/pull/6854
https://github.com/owncloud/ocis/pull/3664
https://github.com/owncloud/ocis/pull/3680
https://github.com/owncloud/ocis/pull/3727
https://github.com/owncloud/ocis/pull/3747
https://github.com/owncloud/ocis/pull/3797
https://github.com/owncloud/web/releases/tag/v5.5.0-rc.6
