[css-typed-om] is2D should be false to serialize with 'translate3d' and true for 'translate'

[arturkulig]

https://drafts.css-houdini.org/css-typed-om/#transformvalue-serialization

is:

• To serialize a CSSTranslate this:
  • If this’s is2D internal slot is true:

should be:

• To serialize a CSSTranslate this:
  • If this’s is2D internal slot is false: