Resolve "DevOps Adoption - Replace mocked data with fixtures"

What does this MR do and why?

This MR replaces the hard coded mock data used for testing the DevOps Adoption frontend with data which is being generated via fixtures.

Screenshots or screen recordings

n/a

How to set up and validate locally

Run the test locally i.e. yarn jest ee/spec/frontend/analytics/devops_report/devops_adoption/

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 #336767 (closed)