Update how-to-run with new rack_network_config subnet (#4948)

docs/how-to-run.adoc

@@ -298,7 +298,7 @@ routes = [{nexthop = "192.168.1.199", destination = "0.0.0.0/0"}]
 # Addresses associated with this port.
 # For softnpu, an address within the "infra" block above that will be used for
 # the softnpu uplink port.  You can just pick the first address in that pool.
-addresses = ["192.168.1.30/32"]
+addresses = ["192.168.1.30/24"]
 # Name of the uplink port.  This should always be "qsfp0" when using softnpu.
 port = "qsfp0"
 # The speed of this port.