Summary: As reported in https://fb.workplace.com/groups/flippersupport/permalink/1171595499987773/, the SupportForm doesn't support dark mode. Fixed this by fixing theming in some of the underlying deprecated components.
Reviewed By: timur-valiev
Differential Revision: D29694034
fbshipit-source-id: f8b90ecc87f7f16f6e1f9751d22309d37a052d5a