Add Gemfile.checksum to jh directory

Related issue: #2932 (closed)

What does this MR do and why?

Related to failed job https://jihulab.com/gitlab-cn/gitlab/-/jobs/7518122

This job failed cause missing Gemfile.checksum file in the jh directory.

Related upstream document https://docs.gitlab.com/ee/development/gemfile.html

Screenshots or screen recordings

Screenshots are required for UI changes, and strongly recommended for all other merge requests.

How to set up and validate locally

bundle exec bundler-checksum init

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.