[css-align] "aligned subtree" isn't a good term for something that isn't a tree

[dbaron]

In inline layout, the term "align subtree" refers to something that's tree-shaped: the layout of an element and its descendants, possibly with some of the descendants excluded.

css-align uses the term to refer to a set of elements in a baseline-sharing group and all of their descendants. There might be other siblings that aren't part of the group, so this isn't a tree, and I think it shouldn't be referred to as one.

[dbaron]

I actually don't think a term is needed here; it can just refer to the boxes in the baseline-sharing group.

[fantasai]

Fixed as requested.