Documentation: networking: Update generic_netlink_howto URL

The documentation refers to invalid web page under www.linuxfoundation.org
The patch refers to a working URL under wiki.linuxfoundation.org

Signed-off-by: Nir Levy <bhr166@gmail.com>
Link: https://lore.kernel.org/all/20221120220630.7443-1-bhr166@gmail.com/
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Documentation/networking/generic_netlink.rst

@@ -6,4 +6,4 @@ Generic Netlink
 
 A wiki document on how to use Generic Netlink can be found here:
 
- * http://www.linuxfoundation.org/collaborate/workgroups/networking/generic_netlink_howto
+ * https://wiki.linuxfoundation.org/networking/generic_netlink_howto