Web: Don't repeat posinset when a list item is split into chunks
Web: Don't repeat posinset when a list item is split into chunks

When presenting the current line, we may have a list item substring,
a string from a descendant element, and then another substring from
that list item. We only want to speak the posinset for the final
list item substring rather than repeating it.

GNOME/orca,GNOME/orca,GNOME/orca,GNOME/orca