Remove unused checkstyle reporting config

The reporting section for checkstyle is not used - mvn site is never
run in CI or documented in release process.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: horgh

pom.xml

@@ -255,26 +255,6 @@
         <japicmp.baselineVersion>4.0.0</japicmp.baselineVersion>
     </properties>
 
-    <reporting>
-        <plugins>
-            <plugin>
-                <groupId>org.apache.maven.plugins</groupId>
-                <artifactId>maven-checkstyle-plugin</artifactId>
-                <version>3.6.0</version>
-                <reportSets>
-                    <reportSet>
-                        <reports>
-                            <report>checkstyle</report>
-                        </reports>
-                        <configuration>
-                            <includeTestSourceDirectory>true</includeTestSourceDirectory>
-                        </configuration>
-                    </reportSet>
-                </reportSets>
-            </plugin>
-        </plugins>
-    </reporting>
-
     <distributionManagement>
         <repository>
             <id>sonatype-nexus-staging</id>