[DOC] - Replace nonstandard unicode bullets (“•” and “▸”) with Markdown bullets

Unicode Bullets: We currently use a lot of unicode bullets (“•” and “▸”), which are not screen reader friendly. I recommend converting these nonstandard bullets to Markdown list bullets.

Per the #devex Slack discussion 1/25, there's no need to preserve the distinctions in type that the two bullet styles currently denote.