[e-acsl] more explicit changelog message

src/plugins/e-acsl/doc/Changelog

@@ -29,7 +29,8 @@ Plugin E-ACSL <next-release>
 Plugin E-ACSL 22.0 (Titanium)
 #############################
 
--* E-ACSL       [2020-11-16] Fix initialization check for heap memory.
+-* E-ACSL       [2020-11-16] Fix soundness bug when checking
+	        initialization of a chunk of heap memory block.
 -  E-ACSL       [2020-10-14] Add Support for Variadic generated functions in
                 the AST (frama-c/e-acsl#128).
 -  E-ACSL       [2020-10-06] Add support for the `\separated` predicate.