Code Insights: Add compute insights to the `changelog.md`

Created by: vovakulikov

It just adds a note to the changelod.md about the compute-powered insight and its experimental feature flag.

Also, it fixes a problem with compute-powered insight on the dashboard page around handling series display filters (sort and limit filters)

Test plan

• Make sure that you can see compute-powered insight on the dashboard page (you can use this dashboard as an example https://sourcegraph.test:3443/insights/dashboards/ZGFzaGJvYXJkOnsiSWRUeXBlIjoiY3VzdG9tIiwiQXJnIjo3MjcyNzV9

App preview:

• Web
• Storybook

Check out the client app preview documentation to learn more.