fix markup nit

Doc/tut/tut.tex

@@ -2767,7 +2767,8 @@ class or function or variable defined in the previous item.
 
 \subsection{Importing * From a Package \label{pkg-import-star}}
 %The \code{__all__} Attribute
-\index{__all__}
+
+\ttindex{__all__}
 Now what happens when the user writes \code{from Sound.Effects import
 *}?  Ideally, one would hope that this somehow goes out to the
 filesystem, finds which submodules are present in the package, and