Enhancement: Update ownCloud Web to v5.3.0-rc.1

Tags: web

We updated ownCloud Web to v5.3.0-rc.1. Please refer to the changelog (linked) for details on the web release.

https://github.com/owncloud/web/pull/6561
https://github.com/owncloud/ocis/pull/3291
https://github.com/owncloud/web/releases/tag/v5.3.0-rc.1
