Update what-is-observability-serverless.mdx to force a build

[scottybollinger]

This is a non-visible change to indicate that the new build pipeline is successful and live on https://www.elastic.co/docs. Safe to merge this once out of draft

[mergify[bot]]

This pull request does not have a backport label. Could you fix it @scottybollinger? 🙏 To fixup this pull request, you need to add the backport labels for the needed branches, such as:

• backport-/d./d is the label to automatically backport to the /d./d branch. /d is the digit NOTE: backport-skip has been added to this pull request.

[elasticdocs]

:rocket: Built elastic-dot-co-docs-preview-docs successfully!

• https://elastic-dot-co-docs-production-cvvyavphs-elastic-dev.vercel.app

• Built with commit bb5b077fff923748600b8c2f7937749146c4a3ab

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