[NEW RELEASE] sonar-checkstyle 9.0.1

Hi,

Short description:
Issue #375: update to checkstyle 9.0.1
Issue #384: update to sonarqube 8.9 LTS

Sonarqube compatibility: 8.9-LATEST
JDK: 1.8

SonarCloud project dashboard: https://sonarcloud.io/dashboard?id=checkstyle_sonar-checkstyle

PR: https://github.com/SonarSource/sonar-update-center-properties/pull/249

Thanks,
Daniel Mühlbachler-Pietrzykowski