[temp.spec.partial.order] Fix index entry: 'more specialized'

The phrase 'more specialized' also applies to variable
templates, not just to class templates.

Author: jensmaurer

source/templates.tex

@@ -3368,7 +3368,7 @@
 
 \pnum
 For two partial specializations,
-the first is \defnx{more specialized}{more specialized!class template} than the second if, given the following
+the first is \defn{more specialized} than the second if, given the following
 rewrite to two function templates, the first function template is more
 specialized than the second according to the ordering rules for function
 templates\iref{temp.func.order}: