Fix wrong markup of an argument in a method signature.

Will backport.

Doc/lib/libctypes.tex

@@ -2088,7 +2088,7 @@ the type.  Some types accept other objects as well.
 \begin{methoddesc}{in_dll}{library, name}
 This method returns a ctypes type instance exported by a shared
 library. \var{name} is the name of the symbol that exports the data,
-\code{library} is the loaded shared library.
+\var{library} is the loaded shared library.
 \end{methoddesc}
 
 Common instance variables of ctypes data types: