[MAINT]: .github/workflows/add_to_octokit_project.yml shouldn't run on forks

[jsoref]

Describe the need

It's incredibly unlikely someone working in a fork of this repository will have a token for this repository and want to use that token in their fork to respond to changes in their fork and update this org's project's board:

https://github.com/check-spelling-sandbox/plugin-create-or-update-text-file.js/actions/runs/7948110380/job/21697748243?pr=1

SDK Version

No response

API Version

No response

Relevant log output

0s
Run actions/add-to-project@v0.5.0
  with:
    project-url: https://github.com/orgs/octokit/projects/10
    labeled: Status: Stale
    label-operator: NOT
Error: Input required and not supplied: github-token

Code of Conduct

• I agree to follow this project's Code of Conduct

[github-actions]

👋 Hi! Thank you for this contribution! Just to let you know, our GitHub SDK team does a round of issue and PR reviews twice a week, every Monday and Friday! We have a process in place for prioritizing and responding to your input. Because you are a part of this community please feel free to comment, add to, or pick up any issues/PRs that are labled with Status: Up for grabs. You & others like you are the reason all of this works! So thank you & happy coding! 🚀

[oscard0m]

According to @nickfloyd's comment, is this something we still want to explore or should we close the issue as 'Not Planned'?