Add info to notify teams around service ping metrics changes to docs

What does this MR do and why?

Update documentation around the lifecycle of service ping metrics with regards to notifying specific groups when metrics are changed / removed. This change clarifies that the Data, Customer Success, and Product Data Intelligence teams need to be made aware of changes to Service Ping metrics so that important reporting doesn't break. Relates to https://gitlab.com/gitlab-data/analytics/-/issues/14587.

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