fix(TableHeader): apply className to outer th node (#1175)
fix(TableHeader): apply className to outer th node (#1175)


joshblack/carbon-components-react,carbon-design-system/carbon-components,carbon-design-system/carbon-components-react,carbon-design-system/carbon-components,carbon-design-system/carbon-components-react,joshblack/carbon-components-react,carbon-design-system/carbon-components