[temp.inst] Add missing \grammarterm.

Misapplication of CWG Motion 11, P4149R1.

Addresses editorial review committee feedback.

Author: tkoeppe

source/templates.tex

@@ -6869,7 +6869,7 @@
 a member of a local class or
 \item
 the function call operator of the closure type
-of a non-generic lambda-expression
+of a non-generic \grammarterm{lambda-expression}
 \end{itemize}
 are instantiated when the declaration of \tcode{F} is instantiated.
 \begin{note}