Arches not listed in "only-arches" continue to serve very old app builds

[kparal]

In FreeFileSync I have flathub.json:

{
  "only-arches": ["x86_64", "i386"]
}

That's because I serve upstream-provided binary builds (because several reasons), and upstream doesn't build for aarch64 or arm. However, other arches were built in the past, when I was building the app directly from source. To my surprise, the app can still be installed from Flathub on aarch64 and arm, but the users receive a very old (2.5 years old) app version. Here's a related bug report.

I'd expect that when "only-arches" or "skip-arches" are configured, then those omitted repos should be purged. Otherwise it can be very confusing for users to receive a years-old build.

Possibly related: #1196

[hfiguiere]

you should remove "i386" anyway.