Fix: remove warning message on cluster UUID retrieval failure with AOSS.

[dblock]

Description

AOSS does not support GET, don't attempt to retrieve cluster UUID

Issues Resolved

Closes https://github.com/opensearch-project/logstash-output-opensearch/issues/186

Check List

• [x] New functionality includes testing.
  • [x] All tests pass
• [x] New functionality has been documented.
  • [x] New functionality has documentation added
• [x] Commits are signed as per the DCO using --signoff

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[dblock]

@dlvenable care to CR?

[dblock]

@dlvenable @oeyh can you please merge? I am not a maintainer.