[Port] [6000.0] Clarify URP 6 index page

Update the URP 6 index page to clarify that the site contains API documentation, but the manual pages have moved.

Jira ticket: https://jira.unity3d.com/browse/DOCG-6191

Author: svc-reach-platform-support

Packages/com.unity.render-pipelines.universal/Documentation~/index.md

@@ -1,8 +1,8 @@
 ---
 uid: urp-index
 ---
-# The documentation has moved to the Unity Manual
+# Universal Render Pipeline (URP) scripting reference
 
-The documentation for the Universal Render Pipeline (URP) in Unity 6 Preview has moved to the [Unity Manual](https://docs.unity3d.com/6000.0/Documentation/Manual/urp/urp-introduction.html).
+The [scripting API](https://docs.unity3d.com/Packages/com.unity.render-pipelines.universal@17.0/api/index.html) documentation is available on this website.
 
-The [scripting API](https://docs.unity3d.com/Packages/com.unity.render-pipelines.universal@17.0/api/index.html) documentation is still on this website.
+The user guide for URP in Unity 6 is in the [Unity Manual](https://docs.unity3d.com/6000.0/Documentation/Manual/urp/urp-introduction.html).