chore: updating link to newer viz plugin blog post (#18707)

* chore: updating link to newer viz plugin blog post

* adding official docs link as well.

* another teensy text tweak

CONTRIBUTING.md

@@ -1116,7 +1116,7 @@ Then, [Updating language files](#updating-language-files).
 
 The topic of authoring new plugins, whether you'd like to contribute
 it back or not has been well documented in the
-[So, You Want to Build a Superset Viz Plugin...](https://preset.io/blog/2020-07-02-hello-world/) blog post
+[the documentation](https://superset.apache.org/docs/contributing/creating-viz-plugins), and in [this blog post](https://preset.io/blog/building-custom-viz-plugins-in-superset-v2).
 
 To contribute a plugin to Superset, your plugin must meet the following criteria: