Remove spurious "\end{description}" that caused formatting to fail.

Doc/ref/ref4.tex

@@ -137,8 +137,6 @@ The \keyword{exec} statement and the \function{eval()} and
 the global and local namespace.  If only one namespace is specified,
 it is used for both.
 
-\end{description}
-
 The built-in functions \function{globals()} and \function{locals()}
 each return a dictionary, representing the current global and local
 namespace respectively.  The effect of modifications to these