docs: update toggle docs

A variety of updates were made to improve the toggle documentation:
* Added comments to help ensure that the waffle(), waffle_switches(),
  waffle_flags() anti-pattern won't be contagious (copied).
* Some minor toggle_description updates.
* Removed empty toggle_target_removal_date annotations for
  non-temporary toggles.
* Removed empty optional toggle_warnings annotations.
* Removed empty optional toggle_tickets annotations.
* Removed deprecated toggle_category, toggle_status,
  and toggle_expiration_date annotations.
* Fixed some indents, use cases, and implementations.

ARCHBOM-1721