Pass source_branch to fix_pipeline when we are in an MR

The fix_pipeline flow is currently not working on production. here is an example agent session that ran the commands, but no MR was created. Upon investigation, the commit step is returning an error because no changes were being made.

I checked the branch for the workload, and it doesnt look like the branch for the MR was being used for the job.

I think we need to pass source_branch when the workflow is started, similar to this curl command. This way the job will be on the branch, and the flow will have access to the MR changes.