Prow cherry-pick component next update needs attention.

[purelind]

After synchronizing the upstream updates （REF https://github.com/ti-community-infra/prow/pull/21）, the code of the cherry-pick component has changed.

• There are changes in the judgment and handling of private repositories, and the skipFork parameter needs to be removed during deployment.
• The handling of the Body in cherry-pick PR needs to modify some code in the repository to retain what we need: keep all bodies of the original PR.