[exception] Remove redundant description. Per [res.on.exception.handling]p4,

destructors do not throw unless otherwise specified, and functions declared
noexcept may not throw.

Fixes #339.

Author: zygoloid

source/support.tex

@@ -2644,10 +2644,6 @@
 \effects
 Constructs an object of class
 \tcode{exception}.
-
-\pnum
-\notes
-Does not throw any exceptions.
 \end{itemdescr}
 
 \indexlibrary{\idxcode{operator=}!\idxcode{exception}}%
@@ -2679,10 +2675,6 @@
 \effects
 Destroys an object of class
 \tcode{exception}.
-
-\pnum
-\notes
-Does not throw any exceptions.
 \end{itemdescr}
 
 \indexlibrary{\idxcode{what}!\tcode{exception}}%