Modify `only-jh-check` job to ignore `package.json` and `yarn.lock`

Details

package.json and yarn.lock are going to diverge from upstream, see reason https://gitlab.com/gitlab-jh/gitlab-jh-enablement/-/issues/170 . We need to modify only-jh-check job in jh/.gitlab/ci/only-jh.gitlab-ci.yml to make it not to check package.json and yarn.lock any more