Get rid of "sec:" prefix that slipped into a couple of \label's.

Doc/dist/dist.tex

@@ -345,7 +345,7 @@ the \option{package\_dir} option.
 
 
 \subsection{Describing extension modules}
-\label{sec:describing-extensions}
+\label{describing-extensions}
 
 Just as writing Python extension modules is a bit more complicated than
 writing pure Python modules, describing them to the Distutils is a bit
@@ -887,14 +887,14 @@ runs the subcommands \command{install\_lib},
 \command{install\_scripts}.
 
 \subsubsection{\protect\command{install\_lib}}
-\label{sec:install-lib-cmd}
+\label{install-lib-cmd}
 
 \subsubsection{\protect\command{install\_data}}
-\label{sec:install-data-cmd}
+\label{install-data-cmd}
 This command installs all data files provided with the distribution.
 
 \subsubsection{\protect\command{install\_scripts}}
-\label{sec:install-scripts-cmd}
+\label{install-scripts-cmd}
 This command installs all (Python) scripts in the distribution.