fix name of NewUserspaceEngine in error/comment

It was renamed some time ago.

cmd/tailscale/backend.go

@@ -97,7 +97,7 @@ func newBackend(dataDir string, jvm *jni.JVM, store *stateStore, settings settin
 		DNS:    cb,
 	})
 	if err != nil {
-		return nil, fmt.Errorf("runBackend: NewUserspaceEngineAdvanced: %v", err)
+		return nil, fmt.Errorf("runBackend: NewUserspaceEngine: %v", err)
 	}
 	local, err := ipnlocal.NewLocalBackend(logf, logID.Public().String(), store, engine)
 	if err != nil {

cmd/tailscale/multitun.go

@@ -12,7 +12,7 @@ import (
 
 // multiTUN implements a tun.Device that supports multiple
 // underlying devices. This is necessary because Android VPN devices
-// have static configurations and wgengine.NewUserspaceEngineAdvanced
+// have static configurations and wgengine.NewUserspaceEngine
 // assumes a single static tun.Device.
 type multiTUN struct {
 	// devices is for adding new devices.