21.9: using correct xml version

Correcting the xml version to be consistent with the entries in the DDDB.

It requires bumping up the version for DiskSupport and SlimStaveSupports.

https://atlas-geometry-db.web.cern.ch/atlas-geometry-db/show_tagged_node.php?node_id=NjUwOQ==&tag_id=MTQwOTI4&user=QVRMQVNERF9SRUFERVI=

FYI: @tadej @nstyles