chore: Fix docs-link in README (#3853)

packages/testing/README.md

@@ -2,5 +2,4 @@
 
 This package contains utilities for writing end-to-end tests for Vendure.
 
-For documentation, see [www.vendure.io/docs/developer-guide/testing/](https://www.vendure.io/docs/developer-guide/testing/)
-
+For documentation, see https://docs.vendure.io/guides/developer-guide/testing/