ceph.in: clarify the usage of `--format` in the ceph command

ceph.in: clarify the usage of `--format` in the ceph command

It is not clear to users in the output of `ceph --help` that
the yaml formatter option is only valid for orch commands.

Before:
-f {json,json-pretty,xml,xml-pretty,plain,yaml}, --format {json,json-pretty,xml,xml-pretty,plain,yaml}

After:
-f {json,json-pretty,xml,xml-pretty,plain,yaml}, --format {json,json-pretty,xml,xml-pretty,plain,yaml}
                        Note: yaml is only valid for orch commands

Fixes: https://tracker.ceph.com/issues/53895
Signed-off-by: Laura Flores <lflores@redhat.com>