flatpak package is broken

flatpak package is broken and fails with this error:
```
/app/extra/opt/freedownloadmanager/fdm: error while loading shared libraries: libgssapi_krb5.so.2: cannot open shared object file: No such file or directory
```
Trying [this](https://github.com/flathub/org.freedownloadmanager.Manager/pull/20#issuecomment-2019109731) yields the following error:

```
$ flatpak install --user https://dl.flathub.org/build-repo/92700/org.freedownloadmanager.Manager.flatpakref

error: Can't load uri https://dl.flathub.org/build-repo/92700/org.freedownloadmanager.Manager.flatpakref: Server returned status 404
```

rolling back to previous commits using flatpak also didn't work and failed with and error, so I couldn't roll back

Start by inspecting the Flatpak package definition and the changes discussed in pull request #20, then reproduce the reported missing-library error. Check the package build and the build-repo installation reference; the work is done when the package installs from a valid reference and launches without the reported library error.

Written by the indexing model from the issue text.