todo_janitor.prompt.update_plan.md

Update todo_janitor.plan.md

1. Given the issues not completed

## [ ] Issue2: Use System_to_one_line() in Hgit.py

• Look at the last merged git PRs in master and in the current repo
• Mark the completed issues in todo_janitor.plan.md

2. Given the issues not completed

## [ ] Issue2: Use System_to_one_line() in Hgit.py

• Look at the TODO in todo_janitor.plan.md like

  ### Info
  - Original description:
    `./helpers/hgit.py:406:# TODO(ai_gp): Use system_to_one_line().`
  

• If they were implemented, mark the task as done