ozg-7492 remove unused variable

Jenkinsfile

@@ -101,11 +101,8 @@ pipeline {
             }
             steps {
                 script {
-                    IMAGE_TAG = JAR_TAG
-
                     configFileProvider([configFile(fileId: 'maven-settings', variable: 'MAVEN_SETTINGS')]) {
                         withCredentials([string(credentialsId: 'dependency-track-api-key', variable: 'API_KEY')]) {
-
                             catchError(buildResult: 'UNSTABLE', stageResult: 'FAILURE') {
                                 sh "mvn  --no-transfer-progress -s $MAVEN_SETTINGS io.github.pmckeown:dependency-track-maven-plugin:upload-bom -Ddependency-track.apiKey=$API_KEY -Ddependency-track.projectVersion=${env.BRANCH_NAME} -Ddependency-track.dependencyTrackBaseUrl=https://dependency-track.ozg-sh.de"
                             }