Remove config related to Sonar (#520)

We experimented with using Sonar,
but decided not to continue due to it not working as desired
with our open source workflow.

.github/workflows/check.yaml

@@ -35,18 +35,6 @@ jobs:
       run: tox -e lint
     - name: Run unit tests
       run: tox -e unit
-    - name: Save PR number to file
-      run: echo ${{ github.event.number }} > PR_NUMBER.txt
-    - name: Archive PR number
-      uses: actions/upload-artifact@v4
-      with:
-        name: PR_NUMBER
-        path: PR_NUMBER.txt
-    - name: Archive code coverage results
-      uses: actions/upload-artifact@v4
-      with:
-        name: coverage-report
-        path: ./tests/unit/report/coverage.xml
 
   mocked-plans:
     name: Mocked plans tests