[meta.reflection.names] Fix formatting for 'N'

Fixes NB US 94-201 (C++26 CD).

Author: jensmaurer

source/meta.tex

@@ -3822,7 +3822,7 @@
   Otherwise, \tcode{r} represents a data member description
   $(T, N, A, W, NUA)$\iref{class.mem.general};
   a \tcode{string_view} or \tcode{u8string_view}, respectively,
-  containing the identifier \tcode{\placeholder{N}}.
+  containing the identifier $N$.
 \end{itemize}
 
 \pnum