[skip ci] Fix send email bug on jenkins pipeline failure (#5721)

Signed-off-by: Nquicksilver <zhifeng.zhang@zilliz.com>

build/ci/jenkins/Jenkinsfile

@@ -57,7 +57,7 @@ pipeline {
                     unsuccessful {
                         container('jnlp') {
                             script {
-                                def authorEmail = sh returnStdout: true, script: 'git --no-pager show -s --format=\'%ae\' HEAD~1'
+                                def authorEmail = sh returnStdout: true, script: 'git --no-pager show -s --format=\'%ae\' HEAD'
                                 emailext subject: '$DEFAULT_SUBJECT',
                                 body: '$DEFAULT_CONTENT',
                                 recipientProviders: [developers(), culprits()],