migration: Change qemu_file_transferred to noflush

We do a qemu_fclose() just after that, that also does a qemu_fflush(),
so remove one qemu_fflush().

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-ID: <20230530183941.7223-3-quintela@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>