Revise UI text for Usage Statistics

What does this MR do and why?

Revises UI text in the Metrics and profiling > Usage statistics section of the Admin Area.

This MR also updates the docs to match the updated UI labels.

Screenshots

Before

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After

• Used correct capitalization of 'Service Ping' throughout.
• Phrased the 'Learn more' links as questions, where appropriate.
• Shortened helper text and used present tense.
• Added Oxford comma to second bullet item.

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How to set up and validate locally

http://127.0.0.1:3000/admin/application_settings/metrics_and_profiling

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #330216 (closed)