docs: update SonarCloud badge in README

[tbouffard]

Use the new project key that matches the new repository name. The project was no longer found when using the old project key.

Covers #310

[sonarcloud[bot]]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud