Fixes #171 ("deque::clear() uses undefined behaviour")

doc/container.qbk

@@ -1341,6 +1341,8 @@ use [*Boost.Container]? There are several reasons for that:
 [section:release_notes_boost_1_76_00 Boost 1.76 Release]
 
 * Added [[no-discard]] attribute in all containers to catch bugs related to unused return values.
+* Fixed bugs/issues:
+   * [@https://github.com/boostorg/container/issues/171    GitHub #171: ['"deque::clear() uses undefined behaviour"]].
 
 [endsect]