package/python-networkx: bump to 2.4

package/python-networkx: bump to 2.4

python-networkx wasn't upgraded for a while due to incompatibilities
with setools not supporting versions above 1.11. With the recent version
bump of setools this is no longer true and we can bump python-networkx
to 2.4.

The license checksum had to be updated while bumping the package, but
only the year of the copyright has changed.

Signed-off-by: Antoine Tenart <antoine.tenart@bootlin.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>