Em dash (—) in text style name turned to question mark

First mentioned in #58706: Regression in MuseScore 2—Em dash (—) not supported.

To reproduce:

Go to Style -> Text;
Click New, create a new text style with an em dash (—) in its name;
Click OK, and then OK again in the main Edit Text Styles window;
Reopen Edit Text Styles, scroll down in the sidebar to find the new style.

Result: em dash is replaced by a question mark.