Update cosmic-files to latest

[norepro]

Update cosmic-files to latest

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[norepro]

Marking as a draft because this currently points cosmic-files to https://github.com/norepro/cosmic-files/tree/handle-derived-mime-types . It is created as a test for that change so it appears in D-Bus aware applications like GNOME Boxes.

Once that is merged, we can update the reference to the main branch and get this project a bit more caught up.