[css-overflow-4] 各種更新

define interaction of line-clamp longhands with balance
w3c/csswg-drafts@78cb54e

Refactor the text about block-ellipsis insertion
w3c/csswg-drafts@7e0ee1a

Mark continue:discard at risk
w3c/csswg-drafts@a9d14dd

Author: triple-underscore