eliminate code warning

Author: stefanseifert

tooling/conga-aem-maven-plugin/src/main/java/io/wcm/devops/conga/plugins/aem/maven/allpackage/FileVaultProperties.java

@@ -32,7 +32,7 @@
 /**
  * Read and write properties.xml for FileVault package.
  */
-class FileVaultProperties {
+final class FileVaultProperties {
 
   private final Properties props;