[over.match.class.deduct] Replace "therefrom" with a more common

construction, and more directly talk about the class template for which
we are ultimately performing deduction.

Author: zygoloid

source/overloading.tex

@@ -1657,9 +1657,9 @@
 (considering initializer-list constructors)
 is omitted if the initializer list consists of
 a single expression of type \cv{}~\tcode{U},
-where \tcode{U} is a specialization of the class template
-for which the placeholder names a specialization or
-a class derived therefrom.
+where \tcode{U} is, or is derived from,
+a specialization of the class template
+directly or indirectly named by the placeholder.
 If the function or function template was generated from
 a constructor or \grammarterm{deduction-guide}
 that had an \grammarterm{explicit-specifier},