doc: C++ Addons documentation page fix
There is a small issue in displaying a code block in the C++ Addons documentation page,
the code separator ```cpp is shown in a code block.
Do not update/delete: Banner broadcast message test data
Do not update/delete: Notification broadcast message test data
There is a small issue in displaying a code block in the C++ Addons documentation page,
the code separator ```cpp is shown in a code block.