Remove unnecessary tag override

What this PR dose

• Change default value of jenkins_repo to kubespheredev
• Remove unnecessary tag override

Why we need it

For first action, please see also https://github.com/kubesphere/ks-devops/issues/253.

Then, in fact, the ansible variables defined in download tasks are not directly related to ks-devops tasks. So I removed the some values in roles/ks-devops/templates/ks-devops-values.yaml.j2. Any changes of tag will be in https://github.com/kubesphere-sigs/ks-devops-helm-chart.

Which issue(s) this PR fixes

• Fix https://github.com/kubesphere/ks-devops/issues/253

/kind chore