[Meta] Clean-up repository files that duplicate organization defaults

## ⚠️ NOTE
This issue is [Meta] and contains instructions for engaging with repositories. Please be sure to appropriately separate comments and other interactions between this [Meta] issue and repository issues (almost always the latter is more appropriate).

This issue is labeled 🏁 **status: ready for work** so people can find it and _NOT_ because any work on this [Meta] issue itself is expected

## Problem
Since we established our norms ([GitHub Repo Guidelines — Creative Commons Open Source](https://opensource.creativecommons.org/contributing-code/github-repo-guidelines/)), GitHub has expanded the files that are supported as organizational defaults ([Creating a default community health file - GitHub Docs](https://docs.github.com/en/communities/setting-up-your-project-for-healthy-contributions/creating-a-default-community-health-file)).

Many of our repositories have the following files that duplicate the organizational defaults:
- `CODE_OF_CONDUCT.md`
- `CONTRIBUTING.md`

## Description
1. Identify repositories that need work: [Code search results](https://github.com/search?q=org%3Acreativecommons%20%22Thank%20you%20for%20your%20interest%20in%20contributing%20to%20CC%20Open%20Source!%20This%20document%20is%22&type=code)
2. For each repository:
1. Verify identical files via checksum
2. Create issue in repository
3. Create PR for repository
- Remove duplicate files
- Ensure the organization defaults are mentioned in the `README.md` so they are visible in default repository view (the organization default files are displayed in the auxiliary column of issues and pull requests)
- For an example, see the `README.md` in [creativecommons/index-dev-env](https://github.com/creativecommons/index-dev-env/)

## Additional context
- [creativecommons/.github](https://github.com/creativecommons/.github): _Default templates and guidelines for Creative Commons GitHub repositories._
- [GitHub Repo Guidelines — Creative Commons Open Source](https://opensource.creativecommons.org/contributing-code/github-repo-guidelines/)
- [Creating a default community health file - GitHub Docs](https://docs.github.com/en/communities/setting-up-your-project-for-healthy-contributions/creating-a-default-community-health-file)