[string.op.plus] Fix phrasing of note

Author: jensmaurer

source/strings.tex

@@ -4967,11 +4967,11 @@
 
 \pnum
 \begin{note}
-The usage of \tcode{type_identity_t} as parameter ensures that
-an object of type \tcode{basic_string<charT, traits, Allocator>}
-can always be concatenated to an object of a type \tcode{T}
-with an implicit conversion to \tcode{basic_string_view<charT, traits>}, and
-vice versa, as per \ref{over.match.oper}.
+Using a specialization of \tcode{type_identity_t} as a parameter type ensures
+that an object of type \tcode{basic_string<charT, traits, Allocator>}
+can be concatenated with an object of a type \tcode{T}
+having an implicit conversion to
+\tcode{basic_string_view<charT, traits>}\iref{over.match.oper}.
 \end{note}
 
 \rSec3[string.cmp]{Non-member comparison operator functions}