qapi/block-core: Clean up after removal of dirty bitmap @status

Commit 81cbfd50 (block: remove dirty bitmaps 'status' field)
removed deprecated BlockDirtyInfo member @status.  It neglected to
remove references to its enumeration values from the documentation of
its replacements.  Do that now.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: John Snow <jsnow@redhat.com>
Message-Id: <20230425064223.820979-6-armbru@redhat.com>