[class.dtor] Fix wording about object's lifetime

Author: languagelawyer

source/classes.tex

@@ -2449,7 +2449,7 @@
 \end{note}
 
 \pnum
-Once a destructor is invoked for an object, the object no longer exists;
+Once a destructor is invoked for an object, the object's lifetime ends;
 the behavior is undefined if the destructor is invoked
 for an object whose lifetime has ended\iref{basic.life}.
 \begin{example}