Update CSS Basic UI Level 3 to CandRec spec

[dstorey]

• “add caret-color property, but at risk.”
• “Dropped the padding-box value of the box-sizing property due to no implementation interest from UA vendors.” (supported by FF)
• “::value and ::choices pseudo-elements have been dropped due to insufficient implementer interest.” (supported by IE [::value] and Chrome)
• “Dropped the nav-index property due to lack of implementation interest.”
• “ime-mode explicitly obsoleted.” (supported by IE and FF)
• “Dropped the icon property.”
• “Dropped the icon value of the content property.”
• “XForms-only pseudo-elements dropped.” (seems to be ::repeat-* as they’re not in Selectors L4 or Pseudo-elements module

I’ve left the selectors in this module even though they’ve been moved out as they’re now in Selectors L4, and there is no other L4 modules in this test AFAICT

[LeaVerou]

Thanks!