Code review comment for lp://staging/~mardy/ubuntu-system-settings-online-accounts/simplify-hooks

I added a comment to say that the files are auto-generated.
However, explanations on how to generate them belong to a separate programming guide (a newer version of https://developer.ubuntu.com/en/start/platform/guides/online-accounts-developer-guide/ ). Once we have it ready, we can put its link into the comment.