fix typo: "darness" => "darkness"
fix typo: "darness" => "darkness"

graphicore/fontbakery,googlefonts/fontbakery,moyogo/fontbakery,graphicore/fontbakery,googlefonts/fontbakery,graphicore/fontbakery,moyogo/fontbakery,moyogo/fontbakery,googlefonts/fontbakery