Revert "Adding upgrade test for ElasticSearch (#705)" (#706)

This reverts commit fbe3834.

Author: arihant-confluent

Jenkinsfile

@@ -4,13 +4,4 @@ common {
   upstreamProjects = 'confluentinc/common'
   pintMerge = true
   downStreamValidate = false
-  nodeLabel = 'docker-debian-jdk8'
 }
-
-def upgradeConnectorTest(body) {
-    build job: "confluentinc/connect-comprehensive-test-framework/master/", parameters: [
-                        string(name: 'PLUGIN_NAME', value: 'kafka-connect-elasticsearch'),
-                        string(name: 'BRANCH_TO_TEST', value: env.CHANGE_BRANCH)
-                    ], wait: true
-}
-upgradeConnectorTest{}