[func.require] Clarify which assignment operators

Author: JohelEGP

source/utilities.tex

@@ -13197,8 +13197,8 @@
 and lvalue arguments are delivered as lvalue references.
 A \defn{simple call wrapper} is a forwarding call wrapper that is
 \tcode{CopyConstructible} and \tcode{CopyAssignable} and
-whose copy constructor, move constructor, and assignment operator
-do not throw exceptions.
+whose copy constructor, move constructor, copy assignment operator,
+and move assignment operator do not throw exceptions.
 \begin{note}
 In a typical implementation
 forwarding call wrappers have an overloaded function call