[DOCS] Typo fix for Kibana 8.1.0 release notes (#186353)

[lcawl]

Summary

Backports #186353

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[obltmachine]

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Just comment with:

• /oblt-deploy : Deploy a Kibana instance using the Observability test environments.
• run docs-build : Re-trigger the docs validation. (use unformatted text in the comment!)

[georgewallace]

LGTM