https://drafts.fxtf.org/geometry/#dom-dommatrix-scaleself

scaleSelf() step 6 says:

If scaleZ is not 1 or originZ is not 0 or -0, set is 2D of the current matrix to false.

But the originZ check is redundant because scaleSelf() internally calls translateSelf() in step 1 which does that check already.

I think we can remove the check, thoughts?

cc @bzbarsky