Fix typo and change folder group to www-data

[siliconninja]

Also note: this is a useful resource for the commands for installing Nextcloud which is located at: https://docs.nextcloud.com/server/12/admin_manual/installation/command_line_installation.html

[j8r]

Thanks for your contribution and the link to the docs. By the way chown user: is a shortcut of the equal chown user:user.