flatpak (build_manifest): updated org.freedesktop.Platform runtime version: manifests were using an old 1.6 version of the runtime, this patch fixes them by using the current 18.8 one. Thanks to that, the main_loop.patch which was made because of an outdated version of GLib (see https://github.com/flatpak/flatpak/issues/1899) is not needed anymore and has been removed. Some useless extensions have also been removed from default manifest.

{
    "_build_settings": {
        "package": "sat",
        "wrapped_command": "primitivus",
        "dev_repos": {"type": "hg", "url": "https://repos.goffi.org/sat"},
        "icon": "https://repos.goffi.org/sat_media/raw-file/tip/icons_svg/sat.svg",
        "desktop_file": "org.salutatoi.Primitivus.desktop",
        "appdata_file": "_tpl_org.salutatoi.Primitivus.appdata.xml"
    }
}