Bump example code version to 0.6.0 in README

Author: adrienthebo

README.md

@@ -14,7 +14,7 @@ You can go to the examples folder, however the usage of the module could be like
 ```hcl
 module "vpc" {
     source  = "terraform-google-modules/network/google"
-    version = "0.4.0"
+    version = "0.6.0"
 
     project_id   = "<PROJECT ID>"
     network_name = "example-vpc"