SF bug #719367, string exceptions are deprecated

Remove references to string based exceptions in the doc.
diff --git a/Doc/ref/ref6.tex b/Doc/ref/ref6.tex
index d447f24..a078aa4 100644
--- a/Doc/ref/ref6.tex
+++ b/Doc/ref/ref6.tex
@@ -521,9 +521,8 @@
 \end{productionlist}
 
 If no expressions are present, \keyword{raise} re-raises the last
-expression that was active in the current scope.  If no exception has
-been active in the current scope, an exception is raised that
-indicates indicates that this is the error.
+expression that was active in the current scope.  If no exception is
+active in the current scope, an exception is raised indicating this error.
 \index{exception}
 \indexii{raising}{exception}
 
@@ -545,9 +544,6 @@
 constructor.  The instance so created by calling the constructor is
 used as the exception value.
 
-If the first object is a string, the string object is the exception
-type, and the second object becomes the exception value.
-
 If a third object is present and not \code{None}, it must be a
 traceback\obindex{traceback} object (see section~\ref{traceback}), and
 it is substituted instead of the current location as the place where