libnetwork/iptables: remove unused Ebtables const

This const was added in 8301dcc6d702a97feeb968ee79ae381fd8a4997a, before
being moved to libnetwork, and moved back, but it was never used.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

libnetwork/iptables/firewalld.go

@@ -20,8 +20,6 @@ const (
 	Iptables IPV = "ipv4"
 	// IP6Tables point to ipv6 table
 	IP6Tables IPV = "ipv6"
-	// Ebtables point to bridge table
-	Ebtables IPV = "eb"
 )
 
 const (