Clear font style name for new fonts
Clear font style name for new fonts

The KDE/Plasma theme plugin (or others) may set the font styleName for a
new font. However we want to match the family name with the bold/italic
attributes instead of the stylename.

See #575

equalsraf/neovim-qt,equalsraf/neovim-qt,equalsraf/neovim-qt,equalsraf/neovim-qt