restricted _subsets_ of algebraic datatypes

Co-authored-by: Pavel Avgustinov <54942558+p0@users.noreply.github.com>

Author: ginsbach

docs/language/ql-handbook/types.rst

@@ -493,7 +493,7 @@ Type unions
 Type unions are user-defined types that are declared with the keyword ``class``.
 The syntax resembles :ref:`type aliases <type-aliases>`, but with two or more type expressions on the right-hand side.
 
-Type unions are used for creating restricted versions of an existing :ref:`algebraic datatype <algebraic-datatypes>`, by explicitly
+Type unions are used for creating restricted subsets of an existing :ref:`algebraic datatype <algebraic-datatypes>`, by explicitly
 selecting a subset of the branches of that datatype and binding them to a new type.
 Type unions of :ref:`database types <database-types>` are also supported.