www/nextcloud: 9.0.51 -> 9.0.52

PR: 211007
Changes: https://nextcloud.com/nextcloud-9-update-brings-security-open-source-enterprise-capabilities-and-support-subscription-ios-app/
Submitted by: Piotr Kubaj <pkubaj@anongoth.pl>
Approved by: Loic Blot <loic.blot@unix-experience.fr>