Fix latex typo

Doc/lib/libcontextlib.tex

@@ -11,7 +11,7 @@ This module provides utilities for common tasks involving the
 
 Functions provided:
 
-\begin{funcdesc}{context}func}
+\begin{funcdesc}{context}{func}
 This function is a decorator that can be used to define a factory
 function for \keyword{with} statement context objects, without
 needing to create a class or separate \method{__enter__()} and