[css-cascade-6] Should @scope's <scope-start> & <scope-end> be unforgiving? #10042

As per the discussion log in making has unforgiving in issue #7676, it seemed like the forgiving behaviour was to be restricted to :is/:where. This is reflected in the spec's note.

On the other hand, <scope-start> and <scope-end> currently are specified as <forgiving-selector-list>.