Correct undeploy for users not in triggers beta (#1260)

Previously, this could have failed attempting to use the blocked
list-triggers API to see if there were any triggers (there should not
be any for a user not in the triggers beta, so making this a no-op is
the right solution.

Author: joshuaauerbachwatson

do/serverless.go

@@ -239,7 +239,7 @@ const (
 	// Minimum required version of the sandbox plugin code.  The first part is
 	// the version of the incorporated Nimbella CLI and the second part is the
 	// version of the bridge code in the sandbox plugin repository.
-	minServerlessVersion = "4.2.6-1.3.1"
+	minServerlessVersion = "4.2.8-1.3.1"
 
 	// The version of nodejs to download alongsize the plugin download.
 	nodeVersion = "v16.13.0"