XLIFF 2.1 WD - 5.9.8 title

Hi,

The current title of 5.9.8 is "ITS categories that do not represent metadata after Extraction of content into XLIFF".
In my opinion it's way too long and most of it is irrelevant. The absence of most of those data categories is not related to
extraction: they are just not relevant in XLIFF.

I propose to change the title to "ITS data categories not represented in XLIFF"

-ys