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 Thanks to that, the main_loop.patch which was made because of an outdated version of GLib (see https://github.com/flatpak/flatpak/issues/1899) is not needed anymore and has been removed.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.

$ORIGIN 0.0.127.in-addr.arpa.
$TTL 1D
@     IN SOA  <hostname>.<domain>. <hostname>.<domain>. (
              <date>     ; serial
              28800      ; refresh (8 hours)
              14400      ; retry (4 hours)
              2419200    ; expire (4 weeks)
              86400      ; minimum (1 day)
              )

              NS      <hostname>.<domain>.
1             PTR     <hostname>.<domain>.