crimson/osd/watch: don't print bufferlists

crimson/osd/watch: don't print bufferlists

The bufferlists clutter the logs and don't infrom of anything useful:
```
DEBUG 2023-05-26 23:36:29,780 [shard 2] osd - send_completion sending notify replies: {notify_reply_t{watcher_gid=4220, watcher_cookie=139786421930752, bl=buffer::list(len=0,

)}, notify_reply_t{watcher_gid=4220, watcher_cookie=139786422032096, bl=buffer::list(len=0,

)}}
```

Signed-off-by: Matan Breizman <mbreizma@redhat.com>
(cherry picked from commit 3548489f622c50ccaa1d8c351e420873743ed980)