Remove SonarQube

[fffej]

It's decommissioned as of 16/10/2020. Few people were getting value from it.

• [x] Are you happy for the content of this change to be publicly visible?
• [x] Are all new or updated entries marked as isNew = true?
• [x] Do radar.csv and radar_libraries render correctly when viewed on Github?
• [x] Does the updated tech radar display as you expect?
• [x] Does the updated libraries tech radar display as you expect?

[adrianbanks]

👍