Discard the environment variables via graphic editing mode

Created by: LinuxSuRen

Describe the bug

Discard the environment variables via graphic editing mode.

/area devops /priority high

Versions used(KubeSphere/Kubernetes) KubeSphere: nightly-20210314

Environment This is not an environmental issue.

To Reproduce Steps to reproduce the behavior:

1. Go to the DevOps page
2. Create a pipeline with the Jenkinsfile from below
3. Edit the pipeline with graphic mode, then click the save button
4. Check the Jenkinsfile again.

A sample of Jekninsfile:

pipeline {
  agent any
  
  environment {
    APP = "hello"
  }
  
  stages {
    stage('simple') {
      steps {
        echo "My name is ${params.name}."
      }
    }
  }
}

Expected behavior Do not discard the environment variables.