[css-sizing] Add missing CSS code in examples 6 and 7

[Loirooriol]

https://w3c.github.io/csswg-drafts/css-sizing-4/#cis-scrollbars

Example 6 just has this code:

div {
  width: max-content;
  contain-intrinsic-size: 100px 100px;
  overflow: auto;
}

The element ends up being 100px wide and 100px tall: contain-intrinsic-size provides the max-content width, and also the height.

This only happens when there is size containment. I think the code should have contain: size. Same in example 7.

If the element then ended up with content that was 150px tall, it would show a vertical scrollbar

Why would it show a vertical scrollbar? There is no height nor max-height, so I'm assuming the initial values, which allow the element to grow big enough for the 150px.