[class.dtor] Turn the normatively redundant paragraph into a note

Author: frederick-vs-ja

source/classes.tex

@@ -2270,9 +2270,11 @@
 \end{note}
 
 \pnum
+\begin{note}
 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}.
+\end{note}
 \begin{example}
 If the destructor for an object with automatic storage duration is explicitly invoked,
 and the block is subsequently left in a manner that would ordinarily