chore: remove Jenkinsfile (#20951)

The unit tests are run by circleci and the changelog updates are not working
currently.

Jenkinsfile

@@ -1,66 +0,0 @@
-pipeline {
-  agent none
-
-  stages {
-    stage('Update changelog') {
-      agent any
-
-      when {
-        anyOf {
-          expression { BRANCH_NAME ==~ /^1(.\d+)*$/ }
-        }
-      }
-
-      steps {
-        sh "docker pull jsternberg/changelog"
-        withDockerContainer(image: "jsternberg/changelog") {
-          withCredentials(
-            [[$class: "UsernamePasswordMultiBinding",
-              credentialsId: "hercules-username-password",
-              usernameVariable: "GITHUB_USER",
-              passwordVariable: "GITHUB_TOKEN"]]) {
-            script {
-              if (env.GIT_PREVIOUS_SUCCESSFUL_COMMIT) {
-                sh "git changelog ${env.GIT_PREVIOUS_SUCCESSFUL_COMMIT}"
-              } else {
-                sh "git changelog"
-              }
-            }
-          }
-        }
-
-        sshagent(credentials: ['jenkins-hercules-ssh']) {
-          sh """
-          set -e
-          if ! git diff --quiet; then
-            git config remote.origin.pushurl git@github.com:influxdata/influxdb.git
-            git commit -am 'Update changelog'
-            git push origin HEAD:${BRANCH_NAME}
-          fi
-          """
-        }
-      }
-    }
-
-    stage('64bit') {
-      agent {
-        docker {
-          image 'golang:1.13'
-          args '-e "GOCACHE=/tmp"'
-        }
-      }
-
-      steps {
-        sh """
-				cd $WORKSPACE
-				go mod download
-        """
-
-        sh """
-        cd $WORKSPACE
-        go test -parallel=1 ./...
-        """
-      }
-    }
-  }
-}