Added flatpak remote-modify reference
Added flatpak remote-modify reference

`flatpak remote-modify --collection-id= ` can be use to set the collection ID of the remote server.
I spent quite a while trying to find how to set it, until I found this blog post:
https://blogs.gnome.org/mclasen/2018/08/26/about-flatpak-installations/
flatpak/flatpak,flatpak/flatpak,flatpak/flatpak,flatpak/flatpak,flatpak/flatpak