Fix markup

Doc/lib/libfuncs.tex

@@ -996,7 +996,7 @@ except NameError:
 
 \begin{funcdesc}{reversed}{seq}
   Return a reverse iterator.  \var{seq} must be an object which
-  supports the sequence protocol (the __len__() method and the
+  supports the sequence protocol (the \method{__len__()} method and the
   \method{__getitem__()} method with integer arguments starting at
   \code{0}).
   \versionadded{2.4}