Align triggers for test & sonarqube jobs

* because sonarqube needs the coverage.xml artifact from the test run

.gitlab-ci.yml

@@ -39,7 +39,7 @@ sonarqube-check:
   allow_failure: true
   rules:
     - if: $CI_PIPELINE_SOURCE == 'merge_request_event'
-    - if: $CI_COMMIT_BRANCH == $CI_DEFAULT_BRANCH
+    - if: $CI_COMMIT_TAG =~ /^v\d+/
 
 pypi-release:
   stage: release