LEG-to-DW: diff markup for added text not bold on higher divisions

If text is added and a "diff markup" conversion is to be created, added higher divisions are not bold in the result. They are only underlined. This is due to the fact that the pure higher divisions are bold already, and additional bold makes the boldness disappear.

EXPECTED OUTPUT When adding a higher division, the "diff markup" conversion output should render higher divisions with bold and underline applied.