fix: Consecutive ruby elements cause line overflow
fix: Consecutive ruby elements cause line overflow

Test: https://github.com/vivliostyle/vivliostyle.js/blob/master/packages/core/test/files/ruby-broken-pagination.html

vivliostyle/vivliostyle.js,vivliostyle/vivliostyle.js,vivliostyle/vivliostyle.js,vivliostyle/vivliostyle.js