Issue #417: upgrade to checkstyle 10.3.1

Author: muhlba91

README.md

@@ -21,6 +21,7 @@ Compatibility matrix from checkstyle team:
 
 | Checkstyle Plugin | Sonar min | Sonar max | Checkstyle | Jdk |
 |-------------------|-----------|-----------|------------|-----|
+| 10.3.1            | 9.0       | 9.0+      | 10.3.1     | 11  |
 | 10.3              | 9.0       | 9.0+      | 10.3       | 11  |
 | 10.2              | 9.0       | 9.0+      | 10.2       | 11  |
 | 10.1              | 9.0       | 9.0+      | 10.1       | 11  |

pom.xml

@@ -94,7 +94,7 @@
   </ciManagement>
 
   <properties>
-    <checkstyle.version>10.3</checkstyle.version>
+    <checkstyle.version>10.3.1</checkstyle.version>
     <sonar.version>8.9.0.43852</sonar.version>
     <sonar-java.version>7.2.0.26923</sonar-java.version>
     <maven.checkstyle.plugin.version>3.1.2</maven.checkstyle.plugin.version>