package/iperf3: bump to version 3.13
LICENSE file hash changed, due to year update.
For change log, see:
https://github.com/esnet/iperf/blob/3.13/RELNOTES.md#iperf-313-2023-02-16
Signed-off-by: Julien Olivain <ju.o@free.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>