[common.iter.types] Avoid "defining" typedef-names

Use "determine" instead.

Author: frederick-vs-ja

source/iterators.tex

@@ -5488,7 +5488,7 @@
 
 \pnum
 The nested \grammarterm{typedef-name}s of the specialization of
-\tcode{iterator_traits} for \tcode{common_iterator<I, S>} are defined as follows.
+\tcode{iterator_traits} for \tcode{common_iterator<I, S>} are determined as follows.
 \begin{itemize}
 \item
 \tcode{iterator_concept} denotes \tcode{forward_iterator_tag}