fix: unset bind-all-interfaces on empty value

`dokku network:set --global bind-all-interfaces` (no value) wrote the literal string `false` to the property file instead of unsetting it, so external tooling could not distinguish "explicitly set to default" from "not set". Drop the empty-to-`false` coercion in `CommandSet` so the empty-value path reaches `PropertyDelete` like every other property, and remove the unconditional `TriggerPostCreate` write so new apps consult the global value before falling back to the `"false"` computed default.

plugins/network/subcommands.go

@@ -192,10 +192,6 @@ func CommandSet(appName string, property string, value string, values []string)
 		}
 	}
 
-	if property == "bind-all-interfaces" && value == "" {
-		value = "false"
-	}
-
 	attachProperties := map[string]bool{
 		"attach-post-create": true,
 		"attach-post-deploy": true,