PendingReleaseNotes: add a note about disallowing delegating inodes

Signed-off-by: Venky Shankar <[email protected]>

Author: vshankar

PendingReleaseNotes

@@ -50,6 +50,9 @@
   recommend that users with versioned buckets, especially those that existed
   on prior releases, use these new tools to check whether their buckets are
   affected and to clean them up accordingly.
+CephFS: Disallow delegating preallocated inode ranges to clients. Config
+  `mds_client_delegate_inos_pct` defaults to 0 which disables async dirops
+  in the kclient.
 
 >=18.0.0