Fix markup so this will format again.

Doc/lib/libdatetime.tex

@@ -1363,7 +1363,7 @@ Instance methods:
 \end{methoddesc}
 
 \begin{methoddesc}{astimezone}{tz}
-  Return a \class{datetimetz} object with new \membar{tzinfo} member
+  Return a \class{datetimetz} object with new \member{tzinfo} member
   \var{tz}.
   \var{tz} must be \code{None}, or an instance of a \class{tzinfo} subclass.
   If \var{tz} is \code{None}, \var{self} is naive,