Attempt to downgrade libportal

[mcatanzaro]

In flathub/org.gnome.Epiphany#39, flatpak-external-data-checker attempted to downgrade libportal from 0.6 to 0.5. That's not great.

[gasinvein]

This started to happen last year with GitHub's .../releases/latest API endpoint from time to time - it appears that it can suddenly return a previous release. I can't say that with certainty since I never managed to reproduce this locally.

In order to properly prevent downgrades, I suppose we'll need to keep track of the current version (e.g. by storing it in another x- prefixed property in the manifest) instead of blindly accepting whatever remote data we get.

[dreua]

Instance of #286

[dreua]

Can we close this as duplicate?

[mcatanzaro]

Duplicate of #286