Update cpp/change-notes/2021-08-24-implicit-downcast-from-bitfield.md

Co-authored-by: Jonas Jensen <jbj@github.com>

cpp/change-notes/2021-08-24-implicit-downcast-from-bitfield.md

@@ -1,3 +1,2 @@
 lgtm,codescanning
-* Extend query `ImplicitDowncastFromBitfield` to detect implicit
-  downcast on references
+* The query `cpp/implicit-bitfield-downcast` now accounts for C++ reference types, which leads to more true positive results.