chore(deps): upgrade jenkins-x-plugins/jx-preview to version 0.6.4

from: https://github.com/jenkins-x-plugins/jx-preview

Author: pow-devops2020

pkg/plugins/versions.go

@@ -25,7 +25,7 @@ const (
 	PipelineVersion = "0.7.32"
 
 	// PreviewVersion the version of the jx preview plugin
-	PreviewVersion = "0.6.3"
+	PreviewVersion = "0.6.4"
 
 	// ProjectVersion the version of the jx project plugin
 	ProjectVersion = "0.2.83"