index.rst : Update link to user documentation

Author: RandyTheOtter

doc/index.rst

@@ -8,7 +8,7 @@ Welcome to core-admin's documentation!
 
 This page contains documentation autogenerated from source tree. It includes
 manpages and API documentation. For primary user documentation, see
-`https://wiki.qubes-os.org <https://wiki.qubes-os.org>`_.
+`https://www.qubes-os.org/doc/ <https://www.qubes-os.org/doc/>`_.
 
 .. toctree::
    :maxdepth: 2