Clean up old compliance report code

What does this MR do and why?

This MR removes all the code that is no longer used after [Feature flag] Enable compliance violations report (!83959 - merged) has been merged.

As seen in that MR, the code path to access the old dashboard was removed.

It also updates mock_data.js to make sure it isn't using old non-GraphQL data.

Screenshots or screen recordings

N/A

How to set up and validate locally

1. Go to [GDK_HOST]/groups/[GROUP]/-/security/compliance_dashboard
2. Validate that the violations are shown
   • If no violations are shown then you can run FILTER=compliance_report_violations rake db:seed_fu to populate violations locally

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 [Feature flag] Enable compliance violations report (#346266 - closed)