[8.5](backport #1488) action: validate changelog fragment

[mergify]

This is an automatic backport of pull request #1488 done by Mergify.

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[elasticmachine]

💚 Build Succeeded

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• Start Time: 2022-10-13T13:40:45.329+0000

• Duration: 17 min 30 sec

Test stats 🧪

Test	Results
Failed	0
Passed	4971
Skipped	17
Total	4988

💚 Flaky test report

Tests succeeded.

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To re-run your PR in the CI, just comment with:

• /test : Re-trigger the build.

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• run end-to-end tests : Generate the packages and run the E2E Tests.

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[elasticmachine]

🌐 Coverage report

Name	Metrics % (covered/total)	Diff
Packages	97.333% (73/75)	👍
Files	67.797% (160/236)	👍
Classes	68.182% (315/462)	👍
Methods	52.471% (892/1700)	👍
Lines	38.776% (9615/24796)	👍 0.012
Conditionals	100.0% (0/0)	💚