docs: remove advanced ql topic about determining specific types

(cherry picked from commit 3d90f6f)

Author: james

docs/language/learn-ql/advanced/advanced-ql.rst

@@ -11,5 +11,4 @@ Advanced QL
 Topics on advanced uses of QL. These topics assume that you are familiar with QL and the basics of query writing.
 
 -  :doc:`Choosing appropriate ways to constrain types <constraining-types>`
--  :doc:`Determining the most specific types of a variable <determining-specific-types-variables>`
 -  :doc:`Monotonic aggregates in QL <monotonic-aggregates>`