[Metric threshold] Fix bug in loading the metric threshold alert details page

[maryam-saeidi]

Similar #175922

Summary

Fix the metric threshold alert details page by removing unnecessary dependencies.

Note
This page is disabled behind this feature flag: xpack.observability.unsafe.alertDetails.metrics.enabled

Before	After

[apmmachine]

🤖 GitHub comments

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Just comment with:

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

[kibana-ci]

💛 Build succeeded, but was flaky

• Buildkite Build
• Commit: 83c5c66

Failed CI Steps

• FTR Configs #6

Metrics [docs]

Async chunks

Total size of all lazy-loaded chunks that will be downloaded as the user navigates the app

id	before	after	diff
infra	1.4MB	1.4MB	-2.0B

To update your PR or re-run it, just comment with:
@elasticmachine merge upstream

cc @maryam-saeidi