suite: thrash old client ignore list expend

The thrash-old-client suite is expected to generate
a few warnings that can be safely ignored.

Fixes: https://tracker.ceph.com/issues/67970
Signed-off-by: Nitzan Mordechai <[email protected]>

Author: NitzanMordhai

qa/tasks/thrashosds-health.yaml

@@ -30,4 +30,5 @@ overrides:
       - out of quorum
       - noscrub
       - nodeep-scrub
+      - Degraded data redundancy
       - is down