[temp.constr.concept] Add a reference for "normal form".

Author: burblebee

source/templates.tex

@@ -1828,7 +1828,8 @@
 the immediate context of the constraint\iref{temp.deduct.general},
 the constraint is not satisfied.
 Otherwise, let \tcode{CI$'$} be
-the normal form of the concept-id after substitution of \tcode{C}.
+the normal form\iref{temp.constr.normal} of the concept-id
+after substitution of \tcode{C}.
 \begin{note}
 Normalization of \tcode{CI} might be ill-formed; no diagnostics is required.
 \end{note}