missing itsm namespace in extension points prose

Missing itsm namespace on core extension points prose

Hi all, I noticed that the core and module extension points prose
descriptions list
only https://www.w3.org/2005/11/its/
as the explicitly allowed ITS Module namespace.
Since the ITS Module is now using both the its and the itsm namespaces,
also the urn:oasis:names:tc:xliff:itsm:2.1
namespace needs listed.
1. Since both namespaces have their xsd among the currently reviewed
validation artifacts and
2. both namespaces are also used for validation from the current Schematron
schemas and since
3. according to OASIS policy machine readable artifacts have precedence
over prose in case of conflicts,
[ergo]--------------------------------
4. fixing this omission can be deemed editorial in nature.

Hereby I propose that the urn:oasis:names:tc:xliff:itsm:2.1 is added where
it's missing in the prose descriptions of the extension points. E.g. file,
group, unit, mrk, sm, match..