[Bug #1576348] Fix typo in example

Doc/inst/inst.tex

@@ -632,7 +632,7 @@ Note that these two are \emph{not} equivalent if you supply a different
 installation base directory when you run the setup script.  For example,
 
 \begin{verbatim}
-python setup.py --install-base=/tmp
+python setup.py install --install-base=/tmp
 \end{verbatim}
 
 would install pure modules to \filevar{/tmp/python/lib} in the first