tf-sync-github-repos.yaml: run production script

1. The job should download the script from the production repo not
   the staging repo
2. The environment variable for the job trigger project branch
   should be "GERRIT_REFNAME" not "GERRIT_BRANCH" [1][2]

[1]: https://ci.trustedfirmware.org/job/tf-sync-github-repos/396/console#:~:text=Komlev%40arm.com%3E-,GERRIT_REFNAME,-%3Dmain%0AGERRIT_EVENT_HASH%3D433740766
[2]: https://javadoc.jenkins.io/plugin/gerrit-trigger/com/sonyericsson/hudson/plugins/gerrit/trigger/hudsontrigger/GerritTriggerParameters.html

Signed-off-by: Arthur She <arthur.she@linaro.org>
Change-Id: Ib5df3f4e0946ec4b0435264b4859916489751622
2 files changed