A new enough libfdt is included in all of Debian 11, Ubuntu 20.04
and MSYS2.  It has also been included for several minor releases
in Fedora and openSUSE Leap, as well as in CentOS.  Therefore
there is no need anymore to ship the sources together with the QEMU
tarballs.

Keep the wrap file so that it can be used with --enable-download,
but do not ship the sources anymore with either archive-source.sh
or make-release.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>