Updated headings and added resources to Customer Health Scoring page

Why is this change being made?

Per issue #1744 :

• Changed heading for Scoring Methodologies to H2
• Changed heading for Account Health to H2
• Changed heading for PROVE components to H2
• Removed Success Criteria section
• Added references from How to Use Product Usage Reporting page to References section of this page

Author Checklist

• Provided a concise title for this Merge Request (MR)
• Added a description to this MR explaining the reasons for the proposed change, per say why, not just what
  • Copy/paste the Slack conversation to document it for later, or upload screenshots. Verify that no confidential data is added.
• Assign reviewers for this MR to the correct Directly Responsible Individual/s (DRI)

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