docs: update discoveryengine v1 docs link (#9512)

Author: diegomarquezp

java-discoveryengine/.repo-metadata.json

@@ -1,7 +1,7 @@
 {
   "api_shortname": "discoveryengine",
   "name_pretty": "Discovery Engine API",
-  "product_documentation": "https://cloud.google.com/discovery-engine/docs/introduction",
+  "product_documentation": "https://cloud.google.com/discovery-engine/media/docs",
   "api_description": "A Cloud API that offers search and recommendation discoverability for documents from different industry verticals (e.g. media, retail, etc.).",
   "client_documentation": "https://cloud.google.com/java/docs/reference/google-cloud-discoveryengine/latest/overview",
   "release_level": "preview",

java-discoveryengine/README.md

@@ -187,7 +187,7 @@ Java 11 | [![Kokoro CI][kokoro-badge-image-5]][kokoro-badge-link-5]
 
 Java is a registered trademark of Oracle and/or its affiliates.
 
-[product-docs]: https://cloud.google.com/discovery-engine/docs/introduction
+[product-docs]: https://cloud.google.com/discovery-engine/media/docs
 [javadocs]: https://cloud.google.com/java/docs/reference/google-cloud-discoveryengine/latest/overview
 [kokoro-badge-image-1]: http://storage.googleapis.com/cloud-devrel-public/java/badges/google-cloud-java/java7.svg
 [kokoro-badge-link-1]: http://storage.googleapis.com/cloud-devrel-public/java/badges/google-cloud-java/java7.html