PendingReleaseNotes: add reference to the new mdsmap max_xattr_size f…

…ield

Signed-off-by: Luís Henriques <lhenriques@suse.de>
(cherry picked from commit b70c752)

PendingReleaseNotes

@@ -555,3 +555,14 @@ Relevant tracker: https://tracker.ceph.com/issues/55521
   (``auth_client_required=cephx`` and ``ms_mon_client_mode=secure``).
   If you have cephx authentication disabled on your cluster, you may
   need to adjust these settings for RGW.
+* Introduced a new file system flag `refuse_client_session` that can be set using the
+`fs set` command. This flag allows blocking any incoming session
+request from client(s). This can be useful during some recovery situations
+where it's desirable to bring MDS up but have no client workload.
+Relevant tracker: https://tracker.ceph.com/issues/57090
+
+* New MDSMap field `max_xattr_size` which can be set using the `fs set` command.
+  This MDSMap field allows to configure the maximum size allowed for the full
+  key/value set for a filesystem extended attributes.  It effectively replaces
+  the old per-MDS `max_xattr_pairs_size` setting, which is now dropped.
+  Relevant tracker: https://tracker.ceph.com/issues/55725