Update `micrometer-metrics.adoc` to indicate requirement for Micrometer-Registry-Prometheus-SimpleClient usage

[Channyboy]

[ramkumar-k-9286]

Hi @Channyboy

Suggested update from #8468 has been added to the page and updated to the draft site.

Please do not merge #8468

Updated draft site link: https://docs-draft-openlibertyio.mqj6zf7jocq.us-south.codeengine.appdomain.cloud/docs/latest/micrometer-metrics.html

Please review the same and add Developer Reviewed label if you are satisfied with the changes.

Regards,
Ramkumar.

[Channyboy]

Looks good @ramkumar-k-9286