Deprecate the `sign-off: create pr from issue` label

[felix91gr]

Now that we have a different workflow from Issue to PR, we should deprecate this label.

Here's the list of things to do before this process is done:

• Eliminate the Label from the catalogue
• Delete the automation that opens PRs when this Label is toggled
• Change the workflow documentation to make this official

[felix91gr]

I've eliminated the Label.

@PLeVasseur do you know how to delete these automations cleanly? I would ask Sam, but IIRC he's on vacation until January.
I bet it's pretty trivial, but I don't wanna break something if I inadvertently leave loose ends.

I'll try to address the workflow docs later today. That part should be fairly straightforward

[PLeVasseur]

I've eliminated the Label.

I would've waited until we merge this first, though so that it's clear on what to do as a contributor:
#251

Not the end of the world if you're able to review and get this merged relatively soon, say within a day or so as you wrote:

I'll try to address the workflow docs later today. That part should be fairly straightforward

[PLeVasseur]

@PLeVasseur do you know how to delete these automations cleanly? I would ask Sam, but IIRC he's on vacation until January.
I bet it's pretty trivial, but I don't wanna break something if I inadvertently leave loose ends.

Theoretically I've tried to keep both the GitHub Actions workflow files and the relevant scripts separate.
Would suggest we at first remove .github/workflows/auto-pr-on-issue.yml.

Once .github/workflows/auto-pr-on-issue.yml is gone, we can then try to remove scripts/auto-pr-helper.py.

[felix91gr]

I would've waited until we merge this first, though so that it's clear on what to do as a contributor:
#251

My bad. I've re-added it. It's letter for letter the same, so I think it should work. I'll review that PR asap