Update README.md

[abhi-singh1105]

Service check is not clearly documented

What does this PR do?

Documents the service check that the conf.yaml provides

integrations-core/teleport/datadog_checks/teleport/data/conf.yaml.example

Lines 170 to 172 in 598ba54

	## @param enable_health_service_check - boolean - optional - default: true
	## Whether or not to send a service check named `<NAMESPACE>.openmetrics.health` which reports
	## the health of the `openmetrics_endpoint`.

Motivation

Doc missing crucial information https://docs.datadoghq.com/integrations/teleport/#service-checks

Review checklist (to be filled by reviewers)

• Feature or bugfix MUST have appropriate tests (unit, integration, e2e)
• Add the qa/skip-qa label if the PR doesn't need to be tested during QA.
• If you need to backport this PR to another branch, you can add the backport/<branch-name> label to the PR and it will automatically open a backport PR once this one is merged

[github-actions]

⚠️ Recommendation: Add qa/skip-qa Label

This PR does not modify any files shipped with the agent.

To help streamline the release process, please consider adding the qa/skip-qa label if these changes do not require QA testing.