fix icx6430 l2 dhcp command

thanks to jorddenn for the report

docs/icx6430.md

@@ -69,7 +69,7 @@ configure terminal
 ```
 Now we turn off the DHCP client, so it doesn't automatically grab an IP and look for a TFTP config (the cause of the earlier timeout messages):
 ```
-ip dhcp-client disable
+no ip dhcp-client enable
 ```
 Now we give the switch its permanent IP address. As the ICX6430 only runs the layer 2 image, we do not assign an IP to a `ve` like usual, we instead assign the switch an IP globally, as well as give it a default gateway (usually your home router/firewall):
 ```