Issue #491: upgrade to checkstyle 10.12.3

Author: muhlba91

README.md

@@ -21,6 +21,7 @@ Compatibility matrix from checkstyle team:
 
 | Checkstyle Plugin | Sonar min | Sonar max | Checkstyle | Jdk |
 |-------------------|-----------|-----------|------------|-----|
+| 10.12.3           | 9.0       | 10.0+     | 10.12.3    | 11  |
 | 10.12.1           | 9.0       | 10.0+     | 10.12.1    | 11  |
 | 10.12.0           | 9.0       | 10.0+     | 10.12.0    | 11  |
 | 10.11.0           | 9.0       | 10.0+     | 10.11.0    | 11  |

pom.xml

@@ -93,7 +93,7 @@
   </ciManagement>
 
   <properties>
-    <checkstyle.version>10.12.1</checkstyle.version>
+    <checkstyle.version>10.12.3</checkstyle.version>
     <sonar.version>8.9.0.43852</sonar.version>
     <sonar-java.version>7.2.0.26923</sonar-java.version>
     <maven.sevntu.checkstyle.plugin.version>1.44.1</maven.sevntu.checkstyle.plugin.version>