Set sonar.python.version parameter for next analysis (#1037)

Author: andrea-guarino-sonarsource

python-frontend/pom.xml

@@ -14,6 +14,7 @@
   <properties>
     <sonar.sources>pom.xml,src/main/java,typeshed_serializer/serializer</sonar.sources>
     <sonar.python.coverage.reportPaths>typeshed_serializer/cov.xml</sonar.python.coverage.reportPaths>
+    <sonar.python.version>3.9</sonar.python.version>
   </properties>
   <dependencies>
     <dependency>