chore(deps): update docker.elastic.co/beats/metricbeat docker tag to v8.18.0

[renovate]

This PR contains the following updates:

Package	Update	Change
docker.elastic.co/beats/metricbeat	minor	8.14.3 -> 8.18.0

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This PR has been marked with label stale Since it has been inactive for 20 days. It will automatically be closed in 10 days if no further activity occurs.