Update the description of bit_appender

Reason: dynamic_bitset does have an append_at_right(), now; it's called
push_front().

Author: gennaroprota

include/boost/dynamic_bitset/dynamic_bitset.hpp

@@ -1401,11 +1401,7 @@ class dynamic_bitset
         //
         // Makes up for the lack of an efficient append at the least
         // significant end: bits are actually appended "at left" but
-        // rearranged in the destructor. From the perspective of client
-        // code, everything works *as if* dynamic_bitset had an
-        // append_at_right() function (possibly throwing the same
-        // exceptions as push_back()) except that the function is in
-        // fact called bit_appender::do_append().
+        // rearranged in the destructor.
         //
         dynamic_bitset & bs;
         size_type        n;