Update links in README

[NoahStebbings]

The links to the radar in the README were broken, this fixes them

• [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] Does radar.csv render correctly when viewed on Github?
• [x] Does the updated [tech radar](https://radar.thoughtworks.com/?sheetId=https%3A%2F%2Fraw.githubusercontent.com%2Fred-gate%2FTech-Radar%2F +++ ADD YOUR BRANCH NAME HERE +++ %2Fradar.csv) display as you expect?

[NoahStebbings]

Actually will fix the redirects, rather than fix this