doc: remove duplicated --max-buckets option desc

[tchaikov]

Signed-off-by: Kefu Chai kchai@redhat.com

[tchaikov]

this should address following build failure of "Docs: build check" job:

Warning, treated as error:
/home/jenkins-build/build/workspace/ceph-pr-docs/doc/man/8/radosgw-admin.rst:527:Duplicate explicit target name: "cmdoption-radosgw-admin--max-buckets".
Build step 'Execute shell' marked build as failure

[joscollin]

@tchaikov You are dropping the first merge of --max-buckets. I'm okay, if that is good. But please see my comment here: #17439

[tchaikov]

I am aware of this, because I'd like to keep the better one.