Fix typo spotted by Detlef Lannert <lannert@users.sourceforge.net>.

Doc/lib/libpyexpat.tex

@@ -118,7 +118,7 @@ Returns a string containing the base set by a previous call to
                                                           encoding}}
 Create a ``child'' parser which can be used to parse an external
 parsed entity referred to by content parsed by the parent parser.  The
-\var{content} parameter should be the string passed to the
+\var{context} parameter should be the string passed to the
 \method{ExternalEntityRefHandler()} handler function, described below.
 \end{methoddesc}