Using 3.28 flatpak runtime
Currently the flatpak manifest uses the 3.28 runtime, which is soon to be outdated by the 3.30 release. The manifest is used to generate the nightly release, which currently doesn't build (due to outdated meson) and isn't really a nightly release, as it's not using the latest runtime.
I already have an MR updating the manifest, but the CI will also need updating if it's going to pass.